As I have exhaustively explained it isn't just occupying a building. It's about the people who are inside that building. In this case congress and the vice president.

There's also an element of symbolism that could embolden similar groups to take over other seats of power.

This isn't about taking over the US Government as it is currently. It is an existential threat to the current paradigm. There's no natural law that says the US must be a federal democratic republic. It could easily be a military dictatorship.

This is all elementary revolutionary stuff.