How was he insubordinate to Hoover and Roosevelt?
As far as Roosevelt, I'm not even sure I know the whole story. Roosevelt let him get away with it, which doesn't make it right. Among other things, The Commander in Chief ordered him to a strategy meeting, and MacArthur just ignored him. MacArthur basically ran his own operation, without bothering to coordinate with Admiral Nimitz or anyone else. Luckily he didn't screw up things badly enough to get in Nimitz' way.