The absence (or scarcity) of available women can definitely contribute to a prevalence of homosexual behaviour among a group of men. There's plenty of historical evidence of that in prisons and on ships during the age of sail. Sex-starved men who are short of the possibility of female company will sometimes fix their attentions on other men (typically younger males who may superficially appear a bit more "effeminate", in that they have less body hair, more delicate features, etc). If so, does it really indicate that the men engaging in such activities are intrinsically homosexual? Or does it rather indicate that they are damned horny, and looking for some kind of outlet wherever they might find it?

Once indulged in, of course, it could become a regular habit. That tends to happen with various types of sexual acts.

There's an emotional basis to sex, and there's a purely physical basis. Both would play a significant part.