Ah, but the feds are involved, and arrests for this seems like a great way to win points with the majorities in Congress. Budget season is coming up, gotta pad your accomplishments!
That's a good point, the ideal strategy might be to do little to stop the events and then later start public high impact investigations and arrests for a few of the involved.
This is what will happen. Arresting them on the spot would have been a mistake for a few reasons (optics for a larger, volatile group, muddying the waters for condermnations of the invasion). Trump is still president for two weeks. I think we'll see action on this on January 21st.