The rally on Jan. 6th served multiple purposes... and remember, the military recruited President Trump to run for office and use those 4 years to "set the stage" with everything they needed to be in place for the culmination of the plan. I won't go so far to say that Trump is merely a figurehead, but it is useful to keep in mind that the military is running the show.

The rally gave the military several things they needed. They had infiltrated the pantifa groups that were invited into the capital by the capital police, so they used that opportunity to collect a lot of valuable info (laptops, storage, etc.) that would have been very difficult to obtain otherwise. Piglosi's laptop may have been worth the whole thing all by itself.

Also, it gave the military the excuse they needed to turn DC into a minimum security prison, and the Dims begged them to do it. There are probably other reasons we don't know about, but those two are obvious. That rally damaged President Trump's credibility badly, so I am pretty sure it was not his idea to do it...