The resistance to providing access to election data in many jurisdictions in 2020 created long lasting suspicions.

It shouldn't have. Access to this sort of data varies from jurisdiction to jurisdiction (as indicated in the below list), but every jurisdiction allows the political parties that run candidates in statewide elections to have access to these lists. Most jurisdictions allow anyone to see the lists, but it's true that some of them have limits on access - but every jurisdiction allows at least the parties to have them:

ncsl.org - Access to and use of voter registration lists

That's the institutional protection against the election shenanigans that conspiracists imagine are happening all around. Because your political opponent has access to all the data, it's impossible to cheat on something as important as, say, Presidential elections. Because they'll check, and you'll get caught. So most people who understand anything about how these processes work understood that there's no opportunity for Democrats to cheat this way without getting caught, because the GOP gets to look at everything.

But that broke down, because you had the de facto head of the GOP saying that the Democrats had cheated. Even though, again, his lawyers were never able to go into court and present to a judge any evidence that they had cheated - and because of the access laws discussed above, Trump's lawyers would have been allowed to access all this stuff. And then you had a bunch of third parties complaining that they weren't allowed to access some of this material, even though - again - the GOP was able to get it. So they went out and created this myth that there was resistance to providing access generally, when it was just resistance to providing access to people and organizations that didn't field candidates in that election.