Exactly. 2020 Polls said Biden was going to win by Reagan 1980-levels.
Uhh... I see something in common, although there are some differences:
Ronald Reagan 43,903,230 50.75% 489 90.9%
James Carter 35,480,115 41.01% 49 9.1%
John Anderson 5,719,850 6.61% 0 0.0%
Joseph R. Biden, Jr. 81,286,358 51.26% 306 56.9%
Donald J. Trump 74,225,839 46.80% 232 43.1%
About 41 million American voters had some problem with a Reagan Presidency, and I would say that the 5.7 million voters for Anderson had a problem with both Carter and Reagan. Add the 41.01% of the vote for Carter and the 6.61% of the vote for Anderson and the Reagan landslide of 1980 isn't quite so impressive as the electoral vote suggests.
OK, as usual the Democratic nominee ran up huge percentages of the vote in a comparatively small number of states in 2020 -- which is what Democrats usually do, and which explains how Donald Trump won against Hillary Clinton in 2016.
Ronald Reagan won "only" 255 electoral votes in which he got an absolute majority of the overall vote. OK, he did win fair and square. Reagan won 24 states (all of those having 8 or fewer electoral votes) and ten by 10% or more over Carter. Remove the Anderson votes from the Reagan margin over Carter and the number becomes a less-impressive 27 states won by 10% or more. Heck, Obama won 20 states by 10% or more in essentially a binary election in 2008.
I could make the case that the differences between 1980 and 2020 were
(1) that Biden ran up the score in the percentage totals in bigger states than did Reagan.
(2) the electorate was more ideologically divided in 2020 than in 1980
(3) there was no third-party nominee taking votes away from the eventual loser in 2020 as there was in 1980, and
(4) the challenger was much closer to losing in 2020 than in 1980.
An even shift of 0.63% in 2020 would have resulted in a 269-269 split in the Electoral College which would have thrown the election to the House of Representatives which Trump would have won. It would have taken about a 5% even swing from Reagan to Carter to allow Carter to win in 1980 had the Anderson vote remained as it was.
We were only an even shift of 0.63% away from the risk of the re-election of the most corrupt, despotic, and devious President ever.
Both had a challenger facing a troubled incumbent, and the challenger won.