Biden has a reputation for being immature, and in this case, Biden is playing out a common Obama and other USA administration tactic, which is to accuse others of what you're doing, yourself. The Obama administration is leaving, disgraced, and is pulling out all the stops in its effort to delegitimize the incoming Trump administration, and to spoil USA relations with Russia and others before Trump becomes the president. It is the Obama administration, and the pathologically-lying CIA and USA intelligence services, who need to grow up. And they should have been grown up at least 8 years ago, but they weren't.

Obama and his admin leave the White House with no legacy to reference. Just about everything notable that Obama did is being reversed or undone, and Obama didn't do all that much that's notable, in the first place. Obama's government is a no-count government. His only legacy will be the dirty actions he pulled, in flagrant disregard of the world, as he was leaving the White House.