What many states? As far as I can find only one state made an election rule change without going through the legislature, that was challenged as unconstitutional, and that was Pennsylvania. They extended the deadline to accept absentee ballots by three days, a change that would benefit both candidates equally. Meanwhile, Trump’s appointee in charge of the Post Office was doing his best to destroy the postal ahead of an election which anticipated a higher than normal number of mail in ballets due to the pandemic. All the ballots received during that extended time were segregated and when counted were not enough to affect the results.I neither accept not reject that the election was stolen in 2020. Biden holds the office of president now, and rehashing the 2020 election will not change that. Many states allowed changes to their voting procedures without going through the legislatures which could be unconstitutional. Also, news about how Hunter Biden's laptop was either squashed or misrepresented as being planted by the Russians by the MSN. The big social media companies cut Trump off from putting out his message which would have allowed him to go around the MSM. So there were some shenanigans going on.
In addition, these nine states made rules or passed laws designed to disadvantage presumed Dem voters.