So I guess in the name of yaoi sex we get two trash human beings who fuck and consequences...

I don't understand why the author couldn't be bothered to just make them both single. It could have worked out great. Especially since the cheaters apparently end up together.

because a majority of yaoi sadly to say aren't about the plot, it's about getting to see fan service sex. The plot is secondary to at least making the work worth the read. Also because rely on it being fictional, when there's any real world scenarios it becomes irrelevant for the greater good.