Your numbers regarding the number of counties won is different from what I have recorded. I wish now I had recorded the source of my numbers. I think they were from the New York Times, but I’m not sure.
However, the total vote counts are the same. As you report, Obama won 69,000,000 votes in 2008 and Biden “won” 81,000,000 votes in 2020. That’s a 17% increase.
I looked up the population estimates for the years 2008 and 2020 with the U.S. Census Bureau data and found that the population grew only 9% during that time, but Biden is supposed to have won 17% more votes, almost double the increase in population. That’s very hard to believe.
After you drop down into the less populous counties (around 30 on the lists), Obama's 2008 vote totals beat Joe's 2020 "vote" totals.
It's clear-cut that they were rigging it somehow. I don't like to speculate on exactly how, but it looks to me like it has something to do with distance from a central point in the affected counties. Like, about an hour's drive [between 40-60 miles].
Everyone looks at the vote totals without looking at the map.