Yeah it's not an std. It's skin contact disease that got spread at a big gay event with lots of skin contact and now it's spreading skin to skin among what I assume are the kind of social circles with gay men partying and clubbing. Since these men are mainly socialising with each other and have limited skin to skin contact outside of this group the spread is mainly staying among gay men.

It also can spread via fabrics and air but is much much more limited spread via those things. So what's happening is mainly based on the very specific social behaviours of gay men.

If it enters straight party/clubbing scenes I suspect it would spread very similarly, it just hasn't found the right person to cause that spread before becoming symptomatic and isolating yet.