Well that is a good question- why didn't Jesus mention incest or bestiality?
Jesus does condemn adultery- repeatedly.
But not incest- not bestiality- not child sex abuse- and not homosexuality.
But Jesus does mention divorce- again in terms of adultery
He answered, “Anyone who divorces his wife and marries another woman commits adultery against her. 12 And if she divorces her husband and marries another man, she commits adultery.”
So all of this does beg the question- why does Jesus focus on adultery- but not homosexuality?
Of course the easiest way you have to deal with it is with a hand wave- 'nothing to see here'- by presuming that 'of course Jesus' was against homosexuality.
And maybe he was- or maybe he just find the issue important like he did adultery.
We do have Jesus's very specific and unambiguous command about divorce though.
According to Jesus- Donald Trump is committing adultery against his first and second wives. And adultery is specifically mentioned in the 10 Commandments.
Now are Christians refusing to recognize Trump's wedding because of his violating Jesus's words?
Not that I have seen.
I think it is clearly an error to assume, as you are trying to do, that just because Jesus did not mention a particular behavior which has been explicitly mentioned else wherein the Bible as being sinful, that he was OK with that behavior. The Bible makes it clear enough that homosexual behavior is a serious evil, on a similar level to adultery. We don't need Jesus to have said so, too.
I imagine that the sins that Jesus felt a need to mention were sins that were common issues among his audience at the time. If incest or bestiality were not commonly occurring, but adultery was, then it'd make sense for Jesus to mention adultery.
Divorce is kind of an odd case. Under the Mosaic law, divorce was allowed. Jesus stated that it was allowed, because of the hardness of their hearts—basically, that the Israelites of the time the Mosaic law was given were not up to living the higher standard, under which divorce would be prohibited. He was addressing an audience that was ready for the higher standard. In fact, that was part of Jesus' purpose, to give a higher standard, a higher law, to his followers, than what had previously been given.
Are we that audience? In our modern society, many of us accept premarital sex, homosexual sex, and other behaviors as acceptable, that clearly would not have been in Jesus' time, nor in the Old Testament times. In some ways, we're at a lower moral level, now, than the ancient Israelites were. Divorce is certainly not a good thing, never to be encouraged, but given how the present generation has hardened its hearts against God, and against God's standards, I think there's little point in expecting divorce to be prohibited. We need to get homosexuality, premarital sex, abortion, and other serious moral issues under control again, before it makes sense to worry about divorce.