Idk, being gay (or any significant deviation from hetero) doesn't make the most sense from an evolutionary perspective, it just seems to be an abnormal behavior that doesn't suit biological survival much
There's tons of conditions that exist that provide a negative affect towards survival, some in
large population percentages. They still exist.
But I read somewhere, someone offered a possible explanation for this: Homoloveuality could be a recessive characteristic, while heterozygous individuals having some sort of advantage over the homozygous dominant. This would be the same as sickle cell anemia: heterozygousity for it gives a resistance against malaria.
There's also the idea that a small percentage of homoloveuality provides a protection against overpopulation
There's also plenty of homos who force themselves to live in a hetero relationship and have had children