There is a legitimate need to purge voter rolls. But it’s supposed to be done after elections, when people have time to respond and keep their registration if there was a mistake.
In the US voting is tied to states because of the electoral college. So if you move to another state you are supposed to register there and drop off the rolls in the state you came from.
Done correctly purges are of people who haven’t voted in that state in the previous presidential election and any election since. This means you have to go years without voting to get purged.
Purging voter rolls right before a contentious ballots of course is not good. And leaves no confidence it was done in good faith