I'd expect anyone going for fraud to attempt to keep it under wraps, give themselves plausible deniability.
If you go all in, get 100%+ turnout for you, have severe transparency issues levied against you and turn more red states blues than would be needed to win, people will stop thinking "He edged his win against Reps" and start thinking "There's clearly something afoot".
It could be conspiracy, fraud, or a very unexpected voter turnout. But any piece of facts that could be put into doubt will raise eyebrows and make people think more and more about fraud.
And it's not everyone. Most people won't ever look into it unless they have to. Local news reporting people being arrested for voter fraud might bring it under scrutiny locally, but as long as any mainstream media don't cover any of this, the average joe will believe no fraud happened because he hasn't seen any of the cracks.
Or the cracks could be hand-drawns. They could be subterfuge to undermine the election and the fraud could be on the other side, or it could be 3rd parties planting the seeds of Chaos.
Who knows, it's not over yet, despite people claiming it is.