They walked into it by abandoning moral values. Same thing that has happened the the apostate mainline churches. They are all on the verge of going under as well.
Episcopal church in my neighborhood sold their “air rights”—a particular favorite in NYC, where you can build a very profitable tall building in a very small space.
You can sell them to the people next door to you.
Now huge skyscraper that looks totally bizarre in our neighborhood blocks the view of the beautiful church from Broadway.
One good thing is that the store on the main floor keeps going bankrupt, no matter what they put in there.
Same with the liberal Jewish denominations (Reform/Conservative) which now have to consolidate their buildings & resources. Most of the members are 50+, LGBT, feminist, or intermarried. (Like the Pittsburgh congregation of recent tragedy.) Probably a good number are not even Jewish, according to Jewish law.
This is sort of a chicken-or-the-egg question. The admission of gays/women, etc. might be the egregious sign of decline. But were these movements in decline anyway, and forced to accept gays/women/left-wing types to artificially inflate their numbers? Or was the admission of gays, women, etc. the catalyst?
Probably a little of both. Once boundaries were eliminated, and the movement lost any moral or philosophical integrity, it became a joke. There was no framework; anyone could join or "identify" with it.
Reform/Conservative Judaism trumpeted proudly how it has openly welcomed gays, and even has a lesbian rabbi currently running their organization. But it's a hollow victory. LGBT people are the only ones left in that movement.