ltdr; Comphet (compulsory heterosexuality) plays an interesting role that is challenging to be completely aware of.
I've experienced this change along with many other women. I think it's a weird and complicated thing and I don't have an answer, but while I think it's possible HRT does some stuff, I also think a lot of it has to do with societal pressures and both internalized transphobia and probably some internalized homophobia as well. We live in a cisheteronormative society and that's where all the pressure lies; we're pressured to believe that our genders are based on our perceived sex and we're also pressured to believe that men belong with women and all of the other baggage that comes along with the heteronormative stuff. Those assumptions reinforce the idea that heterosexuality is the only valid sexuality and lead to subtle but powerful compulsory heterosexuality. The way heterosexuality is lifted up above all other sexualities and incessantly romanticized while other sexualities are considered deviant makes heterosexuality the path of least resistance.