Russiagate was the Democrat's version of "they're defrauding the election". While it's definitely less pathological since there are a lot of factual claims embedded in it, it's basically the same thing, a desperate attempt to rally the party around something to account for the loss that they had convinced everyone wouldn't happen.
The thing is that Russia was using bots and other political influence tools to try and muddy the waters in western politics from about 2013, but the effect was tiny, and it was aimed at supplanting specific institutions like BBC News and CNN with Russia Today, and supporting a handful of radical groups. When this tactic really succeeded was when democrats and neoliberals media turned it into a psychotic conspiracy where Trump was basically receiving direct orders from the Kremlin. It turned everyone who disagreed into a kremlinbot and made people feel like the cold war was happening again.
Russia can hardly influence their own elections properly, and even if it could be proven somehow, I highly doubt that Putin had a significant effect on Trump's win. The entire Russian "influence" tactic is all about pretending to have more behind-the-scenes power than would be provable or even remotely possible, allowing people's fantasies about hidden malignant powers to go crazy.
Have you read the Mueller report? https://www.justice.gov/storage/report.pdf
(I kind of feel like one of those people knocking at the door asking "have you ever heard of our Lord and Savior" whenever I say that)
If you don't want to read the whole document, I suggest you at least read the introduction and executive summary to both volume I and II. Trump did an excellent job at gas lighting people and persuading that he was found innocent, but he really was not. They just couldn't go after him because he refused to collaborate and he is the president. I am curious as to why you think this was a hoax.
There is also a more recent report that is not as well known https://www.intelligence.senate.gov/sites/default/files/documents/report_volume5.pdf
Also, there really wasn't anything even remotely close to what Trump is doing now when he won the election. Hillary Clinton gave her concession speech days after the election, and Obama personally welcomed Trump to the White House, as is tradition.