Right, but isn’t the “main chain” of Ethereum based on a similar principle wherein it’s the main chain because it’s the one the devs use?

No clue, I don't keep an eye on that, I'm partially aware that there are several similar forks (and eth classic was a result of scammy shenanigans) but, afaict, none try to pretend they're the "real" ethereum.

I’m genuinely failing to see a distinction here

A distinction between trust and trustless? Because my initial point was that git isn't trustless, because it works just like any other online system that requires a login, where a central server/database checks if the user sending inputs was properly identified by some mean (password, cryptographic key, something else). Implementing a Merkle or any other hash tree doesn't make something trustless