In addition to being disinherited, discrimination, moving to more expensive bluer areas that are more tolerant, and such that people have already touched on, and I'm sure are significant factors at play, I just kind of want to spitball a couple thoughts. I'm no sociologist or economist or anything of the sort so I don't know how much these thoughts hold water
The sort of stereotypical American dream- husband & wife, 2.5 kids, 2 cars, house in the suburbs, etc. probably looks at least a little different for many LGBTQ people. In many cases, the kids are kind of a non-starter- adoption, IVF, surrogacy, etc. are out of reach for a lot of people for a few different reasons, and if you're not planning around having kids, you may not need that house in the suburbs with a good school district and a yard for them to play in. And if you're not spending money on kids, you may want to spend that money elsewhere, it may be more important to you to be close to other things, or to not have a mortgage hanging over you're head and want to be able to move to a different neighborhood, city, state, or maybe even country every few years when your lease is up.
I'm a fairly stereotypical straight dude, I grew up holding the flashlight for my dad and getting yelled at while he fixed pretty much everything around the house himself, and it gave me a pretty solid foundation as a handyman. There's not much around a house that I'm not confident I could fix myself or with a couple buddies if I needed to, and I suspect that a lot of girls and probably many gay guys have a different experience with that kind of thing in their childhoods. Not that they can't learn those skills on their own later on in life if they want/need to, but it can be a pretty daunting prospect, and I could see a lot of people who didn't grow up learning those skills choosing to live in an apartment or rental house where they can just call maintenance or their landlord when something breaks instead of needing to learn a bunch of plumbing, electrical, carpentry, drywall, etc on the fly as your house is falling apart around you. I'm not sure I'd want to take on home ownership if I had to start from square one and relearn everything I picked up from my dad on my own.