That's how government defeats the double jeopardy clause.
I doubt that the feds would prosecute him for the same crimes that he was just tried for, which were all state level crimes. If so, double jeopardy isn't an issue.
You think so? All it takes is for one person wherever he goes to remember that now iconic face and ask, "Isn't that that kid form Kenosha over there that killed all those people and walked?"
Do you recall the story of former army captain and physician Jeffrey McDonald, who was accused of murdering his wife and two children at Ft. Bragg in the early seventies? I became an intern in the summer of 1981, where he was working as an ER doctor. I hadn't heard of him, but within the first week, somebody pointed him out and told me the story. He had been convicted of the triple murder, but released on appeal on a technicality, and the book (and later movie) Fatal Vision about the crime and trial was written. This is how we all saw this guy - a killer that got away with it (the forensic evidence was pretty compelling, since remarkably, all four members of that family had different blood types).
In any event, McDonald was viewed suspiciously and disapprovingly by much of the hospital staff, but apparently not the hospital management, as they had hired him. He eventually did return to prison, but I suspect that were he a free man today, that story and stigma would follow him. I see the same for this kid. Why would it be any different? Suppose my hospital gave him a nursing job. It would be the same experience for him as it was for McDonald.
I predict that nobody will let him forget.
Some of the Capitol insurrectionists are complaining about being social pariahs wherever they go even if some people around them see them as heroes. They are essentially unhireable according to their own reports. Their legal troubles were nothing compared to what followed.