They were expecting the Capitol Police wouldn't resist or fire on the predominantly white crowd. After all, a bunch of white people storming the Capitol on the day the election is to be certified aren't a threat.
The crowd would capture and subdue the Vice President and Senators responsible for certifying the election. Enough Republicans would capitulate. The election results would not have been certified and alternate
slates of electors would be nominated. The gun stashing seditionists were there as a backup and reinforcement if any politician objected.
They came close. All that they needed to do was have the courage of their convictions.
The ones in front, rush the police and doors and sacrifice themselves for the greater cause.
Lucky for the country, that resolve wasn't there.