The protestors were the agents, not beneficiaries, of the coup, and the path that was sought was intimidating sufficient members of Congress (counting the VP as such) into action associated with, or making sufficient intransigent members unavailable for, the completion of the electoral count to have Trump declared the winner.
> Using the word "insurrection" also portions people for activating the"Insurrection Act" and using military for policing.
If one wanted to use the assault on the Capitol overtly targeting legislators including the Vice President to justify using the military for policing, there’s no reason to use the Insurrection Act, one would simply cite the provisions of the Omnibus Crime Control Act of 1970 regarding “Congressional, Cabinet, and Supreme Court assassination, kidnapping, and assault” (18 USC Sec. 351; which includes attempts) and “Presidential and Presidential staff assassination, kidnapping, and assault” (18 USC Sec. 1751; which includes in its scope both attempts, and completed and attempted acts against the VP); both of which include explicit authority for assistance in enforcement from “from any Federal, State, or local agency, including the Army, Navy, and Air Force, any statute, rule, or regulation to the contrary notwithstanding.” The Insurrection Act is actually much more narrow in the purposes and manner in which the military can be employed.
> Trump supporters had absolutely nothing to gain from storming the capitol
I tend to agree, actually; while it clearly was an attempted self-coup it was a mind-bogglingly ill-conceived attempt.
But they clearly thought they had something to gain, and many of them (including Trump himself on inciting them, framing it as giving courage to members of Congress who he portrayed as secretly supportive in the attempt to detail the count but cowardly without reinforcement from the mob) made very clear what it was: assuring that Biden’s election was overturned and Trump retained power.