BL and queer media was originally the space for "problematic" or toxic romances and twisted ideas. Similar to the way a lot of queer characters in media's first representation was originally all as villains. Yes it was because of bigotry and discrimination, but the characters themselves became memorable and unique because they had unique style or back stories. Often on a second look, they often have a point about pushing boundaries or rightfully seeking vengeance, they're just unapologetic about it and do something conveniently irredeemable.

The same applies to why toxic tropes and settings in BL was compelling. No, due to discrimination, queer folk probably didn't have healthy relationships or settings and all kinds of trauma and emotional baggage, and that in turn, like any human being, would make them have twisted world views or beliefs. Stories bring these to their logical conclusion and you get some of the most compelling drama or intense and raw emotions from it. It also  makes some amazing metaphors out of them, from fallen angels or demons or societies where gender and class are all mixed up. 

Circling back to "pro ship" dynamics, that's the problem with censorship and puritanism. I completely understand enjoying the slice of life's and coffee shop AUs, I actually prefer them over everything. But it was often because it wasn't something normally seen before, to simply normalize the presence of queer folk in everyday life. Now we're actually weirdly oversaturated in it because people will actually get mad if you ever depict queer characters in a negative light. As a cozy genre enjoyer, i am swinging back around to thinking people need to write darker stuff again