I don't think it's as simple as that.
Yes, mass shooters are famous, but they are not "celebrities." People don't follow them as much as they follow say, Kim Kardashian. I think when people say they want to be famous, they yearn for Kardashian-level fame, where millions of people follow your every move. You can't do that when you're dead or in jail. You'd have to be a psychopath to think that that's the route you want, if your main objective is actually fame.
I think there are so many school shootings because
- Parents don't know how or don't bother to keep guns away from minors. I'm not saying no kids should handle guns, I know it depends on the culture, but parents SHOULD KNOW when their kid is handling their gun!
- Kids want an easy solution to their pain, and attacking their real or perceived tormentors is the most obvious way
- Unfortunately, there's precedence. I'm not sure if blaming the media is the right thing to do, but when it's been done before, it's clearly a potential option. When kids are upset, they don't think. They go for what they know.