This is why I think something was going on mentally. He's clearly an incredibly intelligent person; a very logical and thoughtful one. He has to know on that level, that murdering this man isn't going to affect any sort of change. Someone else will merely take his place in that company, and life will go on.
Insurance companies aren't suddenly going to say "you know, he's right. Maybe we should focus less on profits, and focus more on our customers and their health."
Everyone hates health insurance companies. That's nothing new. We all know someone who has been screwed over, if it hasn't happened to us personally [Raises Hand]. But his belief that this would accomplish his stated goal, is just absurd. I think a few years ago he'd agree with this.
Something happened and he underwent a dramatic shift, apparently isolating himself from friends and family, and directing his rage towards this company.
Maybe there will be change down the road, and people at creating that change he wanted. It won't be because he shot a father of two kids in cold blood though.