I'm just spitballing here but I'd bet there's a link between highly militarized movements and patriarchal attitudes due to the material conditions of that kind of struggle. It's not predetermined, of course it can be overcome through self-criticism like what happened in Cuba. But if you're a highly disciplined military outfit I can see machismo being regarded as a value and heteronormativity being praised, even if you are fighting for equality on a theoretical level