It has nothing to do with election integrity.
These are the factors :
1) It has to do with their state law. Mail-in ballots post-marked by election day can still be counted if they arrive by 7 pm that day. You don't have to like it, but it's their law.
2) Due to remote conditions and logistics, 75% of Arizona voters choose to vote by mail-in balloting. Their process is time-consuming.
3) Many ballots are dropped off in person on election day. That leads to a large number of ballots that won't be processed until after the polls close.
4) Then there is the process of "curing," which I don't like .... but Arizona's law provides for it.
Just because you don't like something, doesn't mean that there is fraud at hand. Finally, it simply makes no sense that Kari Lake would be defrauded, and Trump wouldn't be .... when they were on the same ballot. Kari Lake just plain sucks as a statewide candidate in Arizona. Republicans had a great election cycle, but it really should have been one Senate seat better than it was.