Perhaps the drama of Denver. Remember they feel like they have been dissed by the party so what better way to even the score? This isn’t about winning this is all about them.
If the goods on BO come out now, it will give him time to recover before the convention and his voters will forget about it because his handlers will make up all kinds of lies to cover the truth. The later it all comes out the better. The Clinton’s are just playing nice, but have no intention of helping him win. You can bet on that.