and may soon have the majority of the US Supreme Court
Soon? The Supreme Court has been a reliably Republican institution for generations!
The Warren Court has left the building, modern conservative Republicans have had at least a slim majority ever since. And Warren was a Republican too, just from the era when liberal Republicans existed. The problem for the Republicans is that as the Republican party races to more-and-more conservative positions, these lifetime Republican appointees on the court seem more liberal just by keeping to the same positions that got them nominated.
The court’s current swing vote, Anthony Kennedy, is a diehard Reagan Republican. Republicans own this thing already. The trick is that by today’s Republican standards, Reagan was a Communist Kenyan Muslim.
Was it conservative when it said gays have a Constitutional right to marry?
My understanding is that 1) conservatism values limited federal government; and 2) family law is traditionally left to the individual states. And therefore, if a state were to grant someone that right, the federal government would let them. What would be a federal issue is whether someone who is gay got married in one state but another state didn’t recognize it as legally legitimate.