Background was as a big noise church leader in the evangelical tradition. Became liberal in his views, so alienated lots of his former colleagues but endeared himself to advocates of progressive causes.
I have Thoughts about this trajectory, as someone who has been on a reasonably similar one.
I think that Christians from an evangelical background who have moved to a more liberal approach to scripture are often horrified when they look back at the things they used to sign up to regarding sexuality, marriage equality and so forth. Of all the views that one might reassess as one moves to a different expression of faith, that is the one where there's the real possibility of having caused real hurt and harm to people.
So they don't want to make that mistake again, all critical thinking goes out of the window, and they sign up completely to the 'it's just like gay rights' view where trans ideology is concerned.
I see this happening on a denominational level as well as in individuals I know.
The real irony here is that a lot of these people might well have cited evangelical churches' treatment of women as one of the things which made them rethink but concern for women doesn't seem to register in the same way any more. Steve Chalke's list of 'the excluded' in his tweet doesn't include women, yet he came from a bit of the church which absolutely does exclude women, and he knows - or should know - that the patriarchy is a thing.