The first place contributor was the lead maintainer of MultiMC, the project which PolyMC is forked from, and has never been active in the PolyMC fork.
The fourth place contributor is a MultiMC contributor from 2016-2018 who has never been active in this fork.
The fifth place is the MultiMC founder who left in 2017 or so.
So the people he kicked out are the people actively working on the code.
Even just looking at the last year, he kicked out the top 9 contributors while personally being 10th
The guy who kicked them out was focused on pushing political views instead of actually working on code.
And as a bonus, the political view he's trying to push is alt-right edgelordism, which is a step on the modern pathway to actual nazism.
All of the people who contributed significantly have now moved over to https://github.com/PrismLauncher/PrismLauncher, which is a project that isn't going to start making rash decisions based on extremist views.
But it looks like everyone in the commit comments is having fun posting photographs of cats to each other, which I suppose must be some "in joke" of the project. So I guess it's a funny prank they are doing, like an April Fool, but in mid-October.