They were dancing and partying at the thought that they had incited a take over of the US Capitol while they were watching it in a tent near the rally.
Again, where's the proof?? I see none. And I seem to recall reading yesterday that Trumpty first said he'd walk to the Capitol with the rally crowd, but instead returned to the White House.
I believe that if this little party had taken place yesterday, the press would have known about it and would have reported on it.
As far as I can see, the videos at no time show the rioters inside the Capitol.