Clinton lost in 2016 while winning the popular vote because she lost a in a handful of swing states. That is the rules of US elections. Would she have lost without the FBI investigation of her email server? Who knows, but it happened and she lost. Democrats were unhappy, but did not protest or try to stop the ratification of the election.
In 2020 Biden won the popular vote and many of those same swing states. That is primarily the decision of a handful of mid-sized states and they chose Biden, not just NY, CA.
Instead of accepting that as the Democrats did in 2016, they whined like little petulant children all over TV and social media, filed dozens of frivolous lawsuits that all failed for lack of evidence, then tried to line up fake electors, get Pence to break the law, break into voting machines, ask state officials to change vote counts, then called up a mob to led by nazi groups to break into the Capital to stop the ratification. MANY of Trump's co-conspirators have pled guilty to these things including Jan 6 violence. Somehow his supporters refuse to believe it even from those involved.