It would be a lot more difficult to indict a sitting congressperson on something like this, particularly since these can be a plausible argument that whatever they were doing could have simply falled under their official duties.

I think it’s a good move to first go after Trump and the people in his inner circle, because if that conspiracy can be proved in court, it’s an easier lift to then go after the Senators and Representatives who aided it, because one jury already found the conduct to be illegal (and thus not protected in any official capacity).