umm, older people than me can back me up on this
but uhh, how shall I put this?
I am pretty sure 70s "Glam Rock"* was all about creating a safe enviorment for people to express whatever degree of gayness** they might have
sometimes briefly
so Morrissey's interest in such seems obvious don't it?
also, a lot of those bands you listed were pretty effin rad for back then
*=
As opposed to "80s glam rock" which was about homophobic young men dressing up in make-up and likely beating up gay guys or at least ones they percived as being gay. Also, strangely their music is commonly referred to now as "butt rock"
**=in the 70s "gayness" included such stars like the then bi-sexual David Bowie, remember this was before the
gender indenty wars of the 80s had begun...