Its not that its first that is surprising, its that with one exception its only them.
Again: Who else? The rest of the world is in varying degrees of “ass backwards”, especially regarding social issues. Hell, a lot of them aren’t even moving forward but backward.
The thing is that Abrahamic religions were extremely ass backwards on this issue for the longest time. My expectation would be that countries with a majority of atheists or buddhists would never have been as ass backwards about gays in the first place.
IIRC China is supposedly atheist, and so was the Soviet Union, but things were not particularly rosy there either. https://en.wikipedia.org/wiki/LGBT_history_in_the_Soviet_Union
Whether religion or not, it’s often a case of despicable hardliners taking charge and making things worse for pretty much everyone but them.