Xiden had 81 million votes ( more then Obama )

Not unusual... he had a larger voting base and a higher voter turnout.
Every president gets "more votes than the last guy"... because the population and electorate are growing in size.
If I found anything hard to believe, it was that Trump got more votes than he got in 2016. After all of his fuckups on Covid, the economy, civil unrest? What the **** is wrong with you people.
But it does make sense when you factor in growth of the electorate and higher voter participation.
Trump got 46% of the electorate in 2016 and 47% of the electorate in 2020.
Biden got 51% of the electorate in 2020 compared to Hilary's 48%.
Third party candidates got 6% of the electorate in 2016 and 2% in 2020.
So in terms of percentages, there was only a shift of about 4%, and most of that was third party voters who didn't like either candidate in 2016 shifting to picking a candidate who might actually win in 2020.
The reality, though is that even with a record high 66% of the electorate, our voter participation numbers are still pretty pathetic.