I mean... if you think that a method of voting will lead to fraudulent elections, then shouldn't you say something about it?How would you explain Trump's efforts to invalidate the election before it even took place (e.g., telling his voters mail-in ballots would be fraudulent constantly for months before the election)? It seems obvious that he was ready to throw the whole thing into question before voting even started to ensure he could contest a result he didn't like.
Not saying you're wrong about everything else, but this seems to be a silly argument. If Trump though that mail-in voting would result in voter fraud, then it is logical that he would say so. Why would you want to invalidate the results before it takes place? Because you think it's going to be rigged.