Thunk provoking, however while it may be a close contender to being the predecessor of the Troonslop that came after it, I'd wager a decent guess that the games developed by
Puppet Combo are what really got the PS1 slop ball rolling.
Puppet Combo is a game development group founded in 2012 that are most well known for horror games such as Babysitter Bloodbath (2013), Powerdrill Massacre (2015), The Night Ripper (2017), Nun Massacre (201

, among other games they managed to pump out.
Gameplay below of each:
To say that their games "replicate" the PS1 "aesthetic" would be putting it
very generously, as while it features some hallmarks of what made PS1 games look that way (the pixelated + warping textures), they have absolutely no regard for trying to keep it realistic in terms of making it look like a convincing PS1-like (this is especially egregious when there are vent sections in their games and you can see the textures warp as you crawl through, every PS1 gamedev back then would be cringing that PC would let this slide since they didn't WANT that shit in their games and TRIED to mitigate it as much as they could).
They're also infamous for slapping on a VHS filter/static for every game they release, all for aesthetic purposes really but not at all fitting for the timeframe of the console they're "riffing".
I can't say whether or not Puppet Combo are solely responsible for trannies latching onto PS1 graphics, but what I can say is that their games got a lot of eyes on them from Gaming Youtubers, as well as going the Scott Cawthon route of pumping out multiple games yearly.
This is all that they released on their wikipedia page alone:


Now despite all of that I have not heard of any troon developers on their team (then again I hardly know much about them personally other than surface level knowledge of the games they put out), and despite their "attempt" at making "PS1-likes", their games never came off like they were made by troons. Most of them feature 80s slasher film plot points: a serial killer is out committing murder against those who come into contact with them and the victims need to find a way to escape. All presented in a kind of campy way that I cannot say the same for games like ULTRAKILL or Webfishing; despite the latter "supposed" to be kinda campy lol.
I thought I'd bring them up since they're point of interest for this kind of discussion and I want to know if you have anything to say about them; any dramas or info that I'm not aware of since I can't imagine a developer group that's lasted for over a decade go without some kind of shitflinging happening along the way.