He was gambling that R1 was stealing. If he was, then it would have been a legal move to put him out (you can step to an unoccupied base if a runner is attempting to steal). But since R1 didn't go, it's a balk for stepping to an unoccupied base.
@@mikemcdonald9337 if the runner is stealing the pitcher can throw or feint to the base the runner is advancing towards; he does not need to disengage.
He could have stepped to 3rd from the rubber. If there was a runner at 2nd, his move would be legal. If the runner from 1st was clearly advancing to 2nd, his step to 2nd would be legal.
No as long as he steps towards the base he's making a play at. But because the base was unoccupied and the runner from first May have just feinted like he was going but didn't it's a BALK