Have read an opinion of a former NSA agent that he thinks the plan was this.
Trump directs the insurrectionists to the capitol.
When things get violent, and he knew it would, Trump would be there to talk the crowd down and restore order and be seen as the hero.
And then Trump would quickly proceed to call for marshal law which would have delayed the confirmation of the electoral votes.
Sounds wild but feasible I guess.
Here was the plan. There were two "constitutional loopholes" he was trying to get one of. The constitution says Loophole #1 is the power he claimed of state legislatures to declare new electors overriding the voters. That is why he was desperately trying to get DoJ to declare fraud in the election to get states to use that power. Loophole #2 is the 'backup process' for declaring the winner in the constitution:
"The person having the greatest Number of votes for President, shall be the President, if such number be a majority of the whole number of Electors appointed; and if no person have such majority, then from the persons having the highest numbers not exceeding three on the list of those voted for as President, the House of Representatives shall choose immediately, by ballot, the President. But in choosing the President, the votes shall be taken by states, the representation from each state having one vote..."
He was trying to get the process kicked over to that backup process, whether by getting Mike Pence to refuse to accept electors, or by having the mob cause either Pence to go along, or if Pence got killed or driven away from the Capitol for his safety, to have the Senator who replaced Pence in role who was willing to help trump do that, or to disrupt it to go to that 'backup process'.
It wasn't about martial law. It was about trying to use a 'constitution loophole'.
Had that backup process been used, which it may well have been, Republicans had the votes to name him the winner. We came very close to the coup working. 147 Republican in Congress voted to simply steal the election by violating their oath and duty to certify the electors from the states even while they knew they didn't have the votes to get away with it. It could have worked.
When 1/6 happened, my reaction that day was, 'what was the plan, just having this mob go there causing a few hours' delay doesn't make sense as just a spiteful act, probably'.
Now we know. It was to try to invoke that loophole and get the backup process used by preventing the normal counting form completing. It appears some members of Congress were 'in on the plot', and that the information on that conspiracy hasn't all been uncovered. Remember trump's telling DoJ just say it was rigged and leave the rest to him and Republicans in Congress.