Payment processors preventing payment from developers that makes adult games.
This happened because of Collective Shout wanted to get rid of a game called No Mercy (A rape simulation game) on Steam so badly that they forced Paypal and other types of payment processors to ban games that contain anything related to women being hurt or raped.
This affected everything related to games from other platforms and website to get blocked or deleted for being able to sell porn games.
The reason why they change it to get it from a subscribtion site is because their game cant be shown on Itch unless the game does not have payment or donation in it, in order for them to have it stay visible on the store page.
So really, if you wanna blame someone, then blame Collective Shout and the payment processors for ruining everything.
Not exactly, since people had to make their games set as free while having the option to pay be on an external site then Itch.io because of adult games got deindexed if they had payment option in them.
That's why you also dont see any donation in them either.
Some games didn't get affected but other games did because of popularity.
Plus, games that got deindexed would not show on the site to the public unless they were deemed okay to be re-indexed, and that was only plausible if they didnt use payment on their games.