In his own words

 Take it up with Hillary when she's president - I'm outta here

Take it up with Hillary when she's president - I'm outta here

Obama
At a news conference where Russia dominated the discussion, Obama mocked Donald Trump for saying the government accused the Kremlin only after Clinton lost. He argued that his administration was right to slow roll its response to the cyber thefts, in part to avoid charges of inappropriate meddling.
'Stolen emails were already in the possession of Wikileaks, and they were going to come out anyway. The leaks had 'already occurred,' he said.
More aggressive action would have undermined confidence in the election, Obama contended, at a time when Trump was already claiming the voting process was 'rigged'.
'The president said his primary goal was to make sure the 'election itself went off with a hitch, that it was not tarnished and that it did not feed any sense in the public that somehow tampering had taken place.'
'We accomplished that,' he said.

So he and his gang said nothing about the Russians' tampering before the election in order to lull the citizenry into thinking that the election wasn't rigged, but once the election was over, and his side had lost, it is entirely appropriate to undermine confidence in the election and convince the citizenry that the election was rigged.

It's a shame it's too late to try him for treason.