What isn't backed up by the source? The purpose of the mob?
Accepting the government investigation reports, the fake elector plot was real. They didn't _need_ a mob to attack to push Pence into enacting it. It would have just told their story better afterwards.
Optically, if you're going to steal an election by changing which electors count, after putting your own electors in as replacements, then having a mob attack the capital demanding that you respond to some made-up conspiracy is a _lot_ better optics than just enacting the plan without any kind of justification.