The coup attempt was not in the form of the mob themselves taking control. It was the mob trying to disrupt the process of transferring power sufficiently enough to enable or inspire other mechanisms of action. There were, for example, calls for President Trump to declare martial law. It doesn't matter that their plan was vague, poorly coordinated, or unlikely to succeed. They intended to disrupt the transfer of power and executed their intentions violently, injuring over 100 police officers in the attempt. As any number of idiotic criminals in jail can attest to, incompetence in crime does not negate the criminal act.

It also doesn't take nearly as much effort by a mob to accomplish its goals when the people who would help stop it stand idly by: 1) Not enough security was provided in first place 2) Reinforcements took hours to mobilize 3) The President refused to take any action to defuse the situation.