The guy who ran up the tunnel does so every single game. He usually does it with his twin brother, as they get dressed early so they can leave as soon as the coach talks to the team, so they can spend time with their family as they leave that night to go home. His brother stayed behind to talk to a friend on the MSU team this time or he would have been there too.
And there is video of it all from ESPN, CBS, UM security cameras -- It was investigated by the Michigan State Police (as in the state of Michigan, not MSU, though they were involved in the investigation too). They turned their findings over to the Prosecutors office who filed the charges.
The guy on UM that was hit with the helmet and suffered a cut over his eye and a concussion will make more money from this than he did off all his NIL deals in college.