I hope some journalist produces a deep dive into this guy's life history, because this one doesn't make sense. Sure, the manifesto's actual ideas are entirely cribbed from other people; he seems to have just copied ideas he agreed with. But it's written in an articulate way, and shows a self-coherent worldview. Other than the central absurd element (the idea that killing black people would accomplish anything whatsoever for disaffected white men) he doesn't get in his own way.
Usually mass shooters are both crazy and retarded on a personal level; the act itself indicates that the perpetrator hasn't thought through the consequences of their actions, which requires them to be both so disconnected from reality and so slow-thinking that they're incapable of doing that basic cost-benefit about what they're trying to accomplish.
I almost get the vibe that this guy doesn't really believe any of the shit that he's saying, that he's just internalized it from somewhere and regurgitated it. Is there a mental disorder that causes you to internalize ideas and act on them as though they were your own? This guy was clearly smart enough to understand that even among the far right TND was just a meme. Why didn't he kill a government official? That's what intelligent people on the far right say to disavow every race based mass shooting.
I guess my running theory is that this guy had some sort of brain defect that made him copy other people like a parrot, and he was attached to the far right memesphere. He couldn't use his evident reflective capacities to either A: Not commit a mass shooting or B: Kill a politician. The former, because his condition made him lack self-control. The latter, because alt-right communities use racism as a Shibboleth, rather than anti-government sentiment, to weed out individuals sufficiently unmotivated that they aren't willing to risk social ostracization. If he just killed a politician, he wouldn't be a "real" alt-right terrorist.
A lot of mass shooters make their manifesto pay lip-service to the idea of creating political change. Most people assume that this isn't really what they want, because a basic cost/benefit analysis shows that their actions won't lead to the consequences they're looking for. They assume instead that shooters actually want to be notorious, and use the political stuff as a sop to the fragments of their decency that try to stop them. I generally think that this dynamic is an exaggeration, and that the real key is the inability to perform the cost/benefit analysis in the first place. But this guy really challenges my perceptions there, because he's of sound enough mind to ensure that his manifesto is articulate and broadly self-consistent. If he can review a document like this, he should have the capacity to review his own plans. It's almost like he killed those people ironically. But he's not smart enough to have done something that nihilistic; in fact, one of the simplest conclusions to draw from this document is that midwits shouldn't be allowed to participate in the discourse.
Maybe he's just been so internet-poisoned that he couldn't differentiate at an object-level from internet comments and real life interactions. His expectations about the boundaries of human behavior were so set by /pol/, where mass shootings are "part of the conversation" that his lower inhibitions and unwillingness to reflect on his own plans were the result. He'd become so acclimated to a zero-stakes environment that he forgot that killing human beings is a big deal and requires some consideration. It would explain why he only got three, then popped himself when the adrenaline wore off.
But I'm not satisfied with my understanding of things and hope more information comes out.
