They're discussing Russian misinformation campaigns that mislead voters so that they would vote for Trump. That's the illegitimacy they're discussing. Cambridge Analytica and other companies, funded by wealthy doners and PACS spread sophisticated misinformation that discouraged voting and lied about democrats and their policies. This is very different from what Trump's team tried to do, which was to claim that the voting was seriously rigged in the states where he lost. The illegitimacy discussed in those videos are NOT claiming that Russians rigged the voting machines. There are always voting irregularities, for many reasons. Twitter users should try to understand the difference between those 2016 concerns about the misinformation campaigns, which were widely investigated and well known, and what Trump's lawyers tried to prove about voting numbers in states where he lost. Indeed, Trump has spread misinformation and disinformation daily since 2016. He was never presidential in any of his activities. He was illegitimate in his campaign and his role as president, though no one doubts that he was elected.