Man you're fucking stupid if you're anything but a troll or this is a bad joke. The capital building is just a building. Taking control of it does nothing. It's just a good way to destroy a movement. You don't put all of your biggest followers into a group to do something illegal in a way that makes them easy to track and follow, especially when achieving victory still does nothing except getting you arrested or killed a little while after and doing nothing.

Congress can operate operate out of any building. They operate out of that one by tradition. It doesn't hold any power itself. If you take it then now you have control of a perfectly normal building, not something powerful.