Russian interference probably was a small factor in the election, unlike whatever the heck Trump was going on about because his ego is too big to admit losing.
Its hard to say just how much of an impact Russian interference was in the 2016 election, since we don't have the ability to view alternate universes where Russia didn't interfere. And there were certainly a lot of factors involved... Russian Interference, Comey's folly, sexism, incompetent media, etc.
However, one of the keys to Trump's victory was that he won a small number of key swing states by a small handful of votes (less than 1%). It is likely that without Russian interference that Trump probably would have lost those states (and thus the election).