The constitution gives nearly total control of elections to the states, so wouldn’t it make sense for Trump and his allies to be working at the state level? If they are, it seems to be a well-kept secret. Reliving what should have been done in 2020 isn’t going to help one damn bit.
IIRC: Working with states to clean up their voter rolls so that what happened in 2020 was at least mitigated was supposed to Pence's job as chief of a committee. The states wouldn't work with him for the reason you give: it's the job of the states to do that and they didn't want share the work nor disclose how bad things might be. After about six months, Pence gave up on trying and the rest is infamy.