IMO they are tossing Hillary under the bus to protect Obama.
I dismissed this question because Hillary will fire both barrels and every dirty secret she knows at anyone who crosses her BUT I hadn't considered the "Obama Vs Clinton" tug of war in the Dem party. Plausible. Also, dems need some way to get Hillary off the stage, maybe this is the giant hook coming out.
That makes sense except that tossing hillary anywhere is still not that easy to do. Her collection of FBI files probably weighs several tons by now.