(non-US person here)
I hate that I even have to say this, because it seems childishly unnecessary, but I am not a fan of Trump. But I feel there is enough to condemn him for without grasping for straws.
It seems unlikely that he would not have been briefed on the plots that were being organised and the dangers of feeding this crowd that rhetoric.
He has a large responsibility in inciting the level of denial that have led to his supporters to intimidate or threaten officials, many from his own party no less. Allowing this to go for weeks without disavowing or distancing himself publicly has only embolden a crowd that believed in the legitimacy of their actions because the president would not say otherwise.
Maybe we can be generous and say that things got out of hand but that would only show some lack of responsible judgement on his part and I'm not sure it's not somehow even worse.
But the president should have a moral obligation to only talk about actual fraud, not things he wants to have been fraud.
He spent months before the election saying how the postal votes were fraudulent, had his allies set the rules on counting so they would be counted later than other votes (in critical states) and then used that pattern of lots of "late votes" "appearing" as evidence of fraud - when in fact it was the entirely predictable consequences of how it was setup up.