Saving myself the rewrite, I actually made a comment about this very subject a few months ago! You might find it interesting:

Sadly, it’s more like “The rich blew the heads off the poor, and some of the fragments of skull hit the rich in the process.”

Long history of Roman economic prosperity short, the Roman economy was well-developed enough that it experienced growth unheard of before, and would remain unheard of until the 16th century AD. While the rich reaped most of these rewards, as per usual in world history, the structure of the economy meant that a significant amount of benefit still reached the exploited poor, peasants and urban laborers alike.

In the mid-late 3rd century AD, Roman Emperors ruled over an increasingly fragmented empire. Constant civil wars meant that every individual emperor was in a precarious position - and thus had to tread carefully when doing anything that might upset powerful men - such as the army or the aristocracy. The army and aristocracy, realizing their leverage, both used this to intensify their own benefits at the expense of everyone else.

The Emperors Diocletian and Constantine both embarked on massive reform programs over the course of some ~50 years to remove the power of the army, as constant civil wars were immensely costly and destabilizing. They did so by magnifying the power of their own family and clients, and that of… the aristocracy.

For example, one of the reforms of the late 3rd century AD was to bind ultra-poor rural peasants and all of their descendants to their land as coloni, a kind of proto-serfdom. Coloni were not nearly as productive as previous agricultural systems, for the obvious reason that they benefitted very little from their work. Citizenship had been reduced to mean nothing at this time, so the erosion of traditional legal protections did not raise an outcry. This was to make finding conscripts easier (as the army, with the decline of the Roman economy in the 3rd century AD, had become increasingly reliant on forced service instead of volunteers) and making taxation of the peasantry more reliable. Taxing the rich was a non-starter, as internal politics meant that Emperors, in a very unstable position, were very vulnerable to influential men deciding to coup the Emperor - they could not afford to upset men who could have their head put on a stake.

However, as the Empire traditionally did not have a massive bureaucracy, they could collect neither conscripts nor taxes on such a scale on their own - as such, the landowners, local wealthy magnates, were given ever-increasing power over these coloni. As they were given ever-more power over the coloni, they used that power to enhance their own wealth and resources, and cheated the central government - which was reliant on their cooperation - as much as they could. To the point where calls for conscripts often resulted in the landowners sending the least suitable and healthy men to the army, and simple, outright non-payment of taxes.

More beholden to the aristocracy than ever, increasing tax evasion and outright defrauding of the government became more and more difficult to punish. Rather than reverse this, it was decided to intensify it by creating a massive bureaucracy - a step late, one might think - to oversee the land magnates and make sure they did their duty. Of course, this created a massive amount of people who needed to be paid by the central government - and who did they staff the offices with, but scions of the aristocracy? Foxes guarding the henhouse. This also led local authorities to support members of the Imperial family in attempts to seize the position of Emperor or make demands of the central government - as they now had sufficient power to support such coup attempts; whereas previously the risk was from a much smaller pool of Senators and other such high-ranking officials.

Obviously, this solved very little, except creating a massive swathe of men who were beholden to the central government for their sinecures, which more cynical types might suspect was the real intention all along.

These dual burdens of increased taxation/conscription and decreasing rights led many peasants to abandon their loyalty to the Empire entirely - while the disinterest of the poorer classes in the central polity they live in is not abnormal in world history, the Roman Empire traditionally could rely on a great deal of civic loyalty even amongst the relatively poor to bolster its efforts in times of crisis. Instead, now, many peasants became runaways from their position as coloni, paying no taxes and offering no service to the Empire’s armies. Many even became bandits en masse - bagaudae. This turned a military manpower crisis into a military and economic manpower crisis.

But what could they do to stem this? Why, increase punishments for peasants fleeing their duties, of course! And who was to be entrusted with the power to punish these peasants? The men closest, the men who could keep an eye on them - the wealthy landowners they were bound to. Increasing both the dissatisfaction of the peasantry and the ability of the wealthy to resist contributing to the centralized state - as powerful classes act according to what they are capable of doing for their own benefit, not out of gratitude or loyalty or even long-term self-interest.

This ended up creating a massive economic crisis which almost totally demonetized the Roman economy. We take monetization for granted, but it’s really a massive and complex and helpful instrument for transferring resources. Dead. That doesn’t mean “The rich aren’t around anymore”, but rather “Land ownership and personal connections amongst the rich mean more than anything, and the poor find it very difficult to transfer any personal surplus into lasting material gain for themselves”. Price chaos led to similar problems amongst urban laborers, with urban workers scattering from the towns into the countryside to seek work or sustenance; artisans were then bound in a manner similar to coloni to their jobs, which… well, had the same effect as binding coloni to the land. Dissatisfaction, low efficiency, increased power of local authorities, and economic stagnation.

As all of this happened, the central government, unable to meet financial or security obligations, did the only thing it could - reduced spending.

No, wait, sorry, what I meant was “Increased spending on luxuries for the Imperial family and gave massive amounts of wealth and resources to the Christian Church”.

Which, in turn, again, increased the power of local authorities (religious ones, in this case) to resist the central government, and intensified the crisis as a whole. Now barbarians overwhelmed the borders of the weakened Empire, bandits looted the interior, and landlords created private pseudo-armies to protect themselves and loan out to the centralized government when it suited them. All of this made everyone less secure and less prosperous, and ultimately would lead to the total destruction of the Empire in the West.

In the end, many of the wealthy lost everything in the chaos of the Empire’s fall - including their lives. Those who survived did so as minor landowning nobility under barbarian kingdoms which did not have the centralization or experience to maintain the luxuries that the Roman nobility - or probably more accurately, the Roman nobility’s forefathers - had enjoyed. Trade routes dissolved across the Mediterranean, everyday architecture declined drastically, public goods and services once considered normal disappeared; even consumer goods like pottery had massive and centuries-long reversions to pre-Iron Age quality in places. The nobility of this post-Roman world lived like prosperous peasants did in the Empire, and prosperous peasants lived like slaves.

But hey, at least they could maintain private bodyguards to play coup politics in the new kingdoms they lived in, and bully the poors. That’s what matters the most, in the end. I guess.