Thanks for the sincere question. We all (and I am guilty of this for sure) ask too many rhetorical questions because we assume we already know the answers.
I absolutely believe nearly all of the people in the Capitol building were Trump supporters. I believe this because there is ample photo and video evidence, many of the people are being identified by name and their digital footprint makes their loyalties clear.
I posted this yesterday, but it is particularly interesting to look at who was in the Senate Chamber. There are plenty of clear photos and we will know for sure soon enough, but these people do not look like Anifa and in fact the older gentleman is believed to be retired senior military. He certainly looks the part.
Regardless, a number of people have already been identified and none have been shown to be false flag operators.
This of course makes the absolute lies about Antifa told on the floor of the house by Matt Gaetz, and amplified by Fox, absolutely reprehensible.