Two elections ago, the Democratic Party was on the verge of being torn to shreds. After a long series of dirty tricks and one stolen election later, there was an uncomfortable coming together.
Obama and his cronies kept most of the important positions, while the Clintonites got a few pieces of the foreign policy apparatus. The arrangement satisfied no one, but it kept ticking along until the Benghazi attacks happened.
By the time Benghazi happened, Clinton and Obama needed each other more than ever. Obama needed the Clintons on the campaign trail to sell him to more moderate Democrats who remembered that times had been better under Bill. Hillary needed Obama to anoint her as his intended successor.