That was a 500 vote difference out of 6 million votes, a 0.009% difference, in a single state, where there were
known to have been severe issues with the ballots.
Both sides agreed that there were serious issues with the ballots and counting, with the only dispute being how to address them because the issues made it pretty much impossible to determine who actually would have won if the system had been able to correctly register the intended vote of every voter.
There were no serious allegations that anyone did anything illegal or tampered with the votes.
I have a hard time believing that you are seriously comparing that to 2020, where those trying to overturn the election are alleging intentional widespread fraud in multiple states, without being able to offer any creditable evidence that it happened. All the evidence they offer generally falls into three categories:
1. Things that are outright factually incorrect. For example, that video of vote counting in Pennsylvania (I think that was the state...) that supposedly shows suitcases of fake ballots being snuck in and opened late at night.
If you watch the full surveillance video, instead of just that short extract, you see that (1) those are the standard containers they use to store ballots when they are not actively working with them, and (2) those particular ballots were ballots they were working with earlier and put in those containers when they stopped. In other words, all the excerpt is actually showing is the normal resumption of processing after a break.
Another example is the claims that votes were counted without Republican observers allowed in the room, usually based on Republican observers being turned away. Some observers were in fact turned away--because there were already the maximum number of legally allowed observers from their party in the room.
2. Things that are true, but are not evidence of fraud or error. For example, various statistical measures of a candidate's votes look different between the winner and loser in districts where one candidate receives a lot more votes than the other.
They point to these in heavy Biden districts, saying the differences indicate tampering. But if you look at heavy Trump districts, you see the same thing but going the other way.
3. Actual mistakes, such as ballots lost or miscounted. You get some of these in every big election, and no one has found any evidence that these mistakes were more frequent in this election, and even if every single one of this kind of mistake went in Biden's favor, it would not be anywhere near enough to change the outcome in any state.