You see, if it was anybody else they would glow like a supernova, but this is Nick we're talking about, I can almost believe that he's just about retarded enough to do this kind of shit.
But it is odd that he wasn't charged for anything. He was put on a no fly list for a bit though.
A quick search suggests that he might not have personally went inside the Capitol itself, and the feds might be more focused on persecuting the people who trespassed rather than those who merely baited others into trespassing. So he's either a fed, or the kind of coward that has no problem egging others on but chickens out when it's his turn.