Young people are not religious for the most part. Even the ones who say they are Christian don’t go to church and don’t read the Bible. And all the young Republicans are pro-gay.
The future of the Republican party is going to be much more liberal than what it is today. And in some sense, Trump kind of paved the way with his “Gays for Trump” welcoming. He’s far from the only one though of course. You had quite a few Senate and House Republicans vote for homosexual marriage.
It's interesting to observe that Trump was the most socially liberal president since Nixon and no two men were more hated by the Left.