Blame the Russians is probably too convenient to not be used. It is a useful PR story because it has multiple benefits - it deflects blame "don't read the emails, worry about the Russians hiding in the bushes ready to attack instead", and it takes a jab at Putin. Him and Hillary specifically, are not very good friends. They've battled over on Syria ("I'll set a No Fly zone there!"), but goes back probably as far as Bill Clinton involvement in the Balkan Wars. Of course also by Hillary severely criticizing his own rigging of his election.

During the debates, along all the other entertaining stuff I saw (from both sides), I remember Hillary mentioning how not less than 17 intelligence agencies checked and told her it was the Russians. If you listen to the news, that's how you know something is a lie - they overemphasize stuff. If she is saying Coast Guard Intelligence went out of their way to investigate and tell her the Russians did it, you know it is probably time to stop worrying about Russians and worry about other stuff. (Another example, Cuomo from CNN said "it is illegal to read these documents, you have to come to use for interpretation", I knew, those documents have to be read, probably paying close attention...)

Looking at it from technical aspect, I would imagine any state actor who is not stupid, probably managed to hack into that server. Russians are good but they don't somehow have magic others don't have.