What's the point when you can delete or add ballots whenever you please?

I saw an anchor explain that state legislators are responsible for the voting laws. In a federal election, why do we allow states to have different rules? I'm fine for that states election, but for the federal, we should all have the same rules. Like we've had for two centuries. The Dems changed the rules at the 11th hour. They cheated. This will not be resolved for weeks.