I read on the Athletic that it's possible Harbaugh let his team go over to the sideline to celebrate with the student section for a few minutes, to possibly answer your question.
And what is the Michigan player guilty for here? Walking into the tunnel? Come on.
I'm not even much of a Michigan fan; Harbaugh is a semi-jacka$$ at the least, and the fan base is arrogant (much like the fanbase to the east of Ames). But to put the blame on anyone else besides the Spartan players who started a gang assault on one guy is just plain silly.
Yes. Situational awareness is lacking at the least. At worst, he was involved in instigating the altercation. We won't know which without a video that starts earlier.