Obama hates Hillary and never wanted her to win.
He only campaigned for her when he thought that she would win with or without his help. Couldn’t risk pissing her off and then suffer the consequences if she became president.
I always suspected that he would throw her under the bus the minute she showed any weakness.
Obama thinks he is like the dazzling three-point shooter, and Hillary is a low-post dunker. Not pretty, but effective, and a hard competitor. As long as they were playing for the same team, he didn't have much choice to cover her back. But now that it looks like she's about to lose what he thinks was a gift to her, he's a little pissed. He doesn't want to get blamed for this, and now he's backing off. Some friend!
When the going gets tough, Obama kicks you!