I think like everything else it's a spectrum down to personal choice. Some people prefer to be monogamous, others don't. I don't think it matters what humans 'innately' gravitate to, we do all kinds of thing outside our innate nature, so that is neither here nor there.
Heterosexual people have been conditioned for monogamy because it suits the structure of human social bonds since farming was invented probably and we led a more settled lifestyle rather than hunter/gatherer. Whereas homosexual men especially were conditioned in to accepting 'second best' of anonymous or serial encounters mainly out of personal safety and staying under the radar. Both these became fetishized, and now we have the norms we have today.
In reality just like the spectrum of sexuality, some straight people would prefer a more casual sexual lifestyle and some gay people a more monogamous one - feelings are influenced by social norms, but if it was a level playing field, I think we would see a more even split. Much like gender norms.
There is also an element of mental conditioning and 'slave' or colonial mentality about gay men and monogamy, there's a lot of layers to unravel and explore to get to the bedrock of the question - the surface answer of 'gay men can't make babies so we can fuck who we want, when we want' suits some people for a variety of reasons and does not suit others likewise. Personally, I always find it interesting when people tell others what they should be doing because 'everyone else' in their group does it. Says a lot about them.