That's what the Swamp does when it's being drained
Flake almost always votes with Trump's agenda and the rest of the GOP. What Trump doesn't like about him is the fact that he exhibits some amount of independence. Because the GOP under Trump is a fascist party, i.e., you don't go against Il Duce, ever. And that's what draining the swamp really means. It is the counterpart to his attacks on the free press. It seeks to remove opposition to the leader and consolidate power.
Perhaps we should name Trump Augustus Obesus.