All of the people claiming this was fed-instigated or a total false-flag have been on the internet too long and are detached from reality. There is no shortage of people like this guy, the so-called 'signs' that he's an obvious glow are just the inevitable things you see when one guy tries to plan something. This isn't a movie where everything happens in a predictable and logical way.
>muh why did he do his attack like this, I could have planned something way better with my CS:GO experience
There is a certain level of pragmatism involved in these sorts of things, and on top of that the sort of person whose going to do this isn't likely to be particularly smart anyway