By this logic, systemic reason behind "lovesick" teenager shooting former girlfriend is that girls sometimes stop dating boys. Girls should think again before rejecting boys. And black churches should think again about praying, because Dylan Roof had shoot them.
Neither Austin bomber nor Parkland shooter explained why they did it, but whatever they states reasons, the objects of their hate don't necessary have responsibility to obey their wishes.
So no, the "youtube can not demonetize videos" straightforward nonsense is not an analysis of systemic reasons behind this shooting.