You make this sound like it was a democrat plot, it was not.

Thune, the republican senate majority leader, was the one that put up the unanimous consent motion.

There were more than just 5 people there. Though it was late at night.

You can't push something through unanimous consent if there's not a quorum. That requires at least 51% of each party to be present.

Now, it's possible they waited until some of the big objectors to the bill fell asleep or left. But, that doesn't really change the fact that Thune pushed this through.