Like suspiciously stupid. Getting caught, even if you get your manifesto out there, doesn't really help your cause. Disappearing; leaving a constant doubt of a professional killer hunting insurance CEOs would.

So here's hoping Luigi plays along for a couple weeks and goes "haha suckers, here's my alibi."

And, from all accounts, this guy was not stupid - high school valedictorian, high honors in college, tech bro who made or acquired a ghost gun. My guess is the evidence was planted or he wanted to get caught. I mean, it was a ghost gun - he could have melted it down or broke it into pieces, etc. Why would he still have it?

You asked why as a reply to a comment that suggested he wanted to get caught. That would be the why.

Perhaps he wants to have his day in court and air out what these evil companies do.

Maybe he had more than one target, thus he still needed the gun.