I missed anyone on MSN(BC) saying his election was illegitimate. There were questions about it, for sure. There was the essentially incontrovertible fact that he won in the EC without winning the popular vote, which is an unfortunate feature of our system. That does lend a certain sense of "illegitimacy" but not in the sense of something illegal having happened, more a sense of "moral legitimacy". A few weeks after his election, the overwhelming majority of progressives accepted that Trump was the officially elected president of the USA. We didn't like it, but we accepted it.

The issues regarding Russian interference were not centered on collusion, but on ... well, interference (which some believe went so far as to include actual collusion).

Mueller's report and the Senate report did find conclusively that the Russians did interfere, and did so with the goal of getting Trump elected. Mueller said that they did not find evidence of active collaboration between the campaign and the Russians ... here's the current Wikipedia summary:

>did not find sufficient evidence that the campaign "coordinated or conspired with the Russian government in its election-interference activities". Investigators ultimately had an incomplete picture of what happened due to communications that were encrypted, deleted, or not saved and due to testimony that was false, incomplete, or declined. However, the report states that Russian interference in the 2016 presidential election was illegal and occurred "in sweeping and systematic fashion" but was welcomed by the Trump campaign as it expected to benefit from such efforts

Again, I recall essentially nobody in any position of power (certainly not elected Senators) saying the Trump's election was illegitimate. People did say that his election was aided by Russian interference (Mueller and the Senate investigation state this clearly), and that it was/is unfortunate to have a president elected without winning the popular vote.