It's hardly post-hoc. There was no evidence revealed in the emails that revealed anything more damning than that DWS, and the DNC, preferred Clinton (the Democrat) to Sanders (not a Democrat).
She stepped down early, and was replaced with DB, an even bigger Clinton fan.
By July 22nd, the entire party was in unity mode, and Sanders was actively being courted for his endorsement. DWS resigned as a sacrifice play.
As for the email question, it wasn't making an excuse for it, so much as it was pointing out it had no effect on the proceedings.
Either way, I believe this thread shows how little the DNC hack revealed.