It isn't 'strange', it is, as you say, very obviously and intentionally monetized the same way TikTok is.

The 1% huge payoff vs 99% no payoff divide being essentially random is the point.

The draw of potentially going viral and potentially becoming a multi millionaire is what draws in people, particularly young people whose brain's haven't matured yet and thus aren't capable of realistically assessing risk vs reward.

Its gambling, but essentially as an independent contractor career or hobby.

The cost is opportunity cost, your time and attention and work.

Probably many of the people pouring tons of work into Roblox for years now could have just made their own indie games at this point, probably made a lot more money.

https://devforum.roblox.com/t/reminder-about-ip/116517

Here the official Roblox account on their own forums clarifies that anyone making a Roblox game is inherently giving Roblox a liscense to use all of their IP.

So... if you proof of concept something in Roblox, it gets decently popular, and then you decide eh, im gonna pull the gamemode out of Roblox after I develop something similar in Unity or Godot or something... does... Roblox retain some amount of rights and is now able to sue you?

Does Roblox even honor the request to withdraw your Roblox game?

I am genuinely asking these questions, I am not able to find examples or guidelines for these scenarios/hypotheticals.

Tons and tons of the software industry revolves around who technically owns the right to exactly what ideas, what code, what formats... and the entertainment industry is similar with character likenesses, plot lines, etc.