I'm not going to go back and watch the speeches of each of those senators to find out why they voted it down, but I'll take a guess that it was because the bill is written to overrule states rights.
Rubio said this: "it is unnecessary, there are other priorities, and this is an issue he’s always believed should be handled by the states."
And Cruz said this: "The way the Constitution set up for you to advance that position is convince your fellow citizens that if you succeeded in convincing your fellow citizens, then your state would change the laws to reflect those views. In Obergefell, the court said, 'No, we know better than you guys do, and now every state must, must sanction and permit gay marriage,'” Cruz continued"
So, I'm sure you have all the links, did any of those that voted against it say they did so because they didn't think gay marriage should be legal, at all, or did they all cite states rights?
Look, I'm not denying that there ARE people against gay marriage, I don't think they will prevail in their efforts.