Doom1UPDATE: The guy said in his manifesto that his plan existed long before Trump's presidency, but that he knows Trump's thetoric will get the blame anyways.
Picture this: You've wanted to touch the stove top for a long time. A real long time. Then, one day, someone with authority says "some fine people have touched the stovetop" or laughs and smiles when you suggest touching the stove. Yes, your desires predate this guy talking about the stove, but he's the one encouraging you. It's been said in this thread before: Trump is not the cause of the shooting, but he's no hindrance either.
https://theintercept.com/2019/08/04/el-paso-dayton-mass-shootings-donald-trump/
Obviously, the shooter must've spent some time on 8chan if he felt it appropriate to post his manifesto there, so his views were probably reinforced there, and if he watched cable news he'd have found a friend in Tucker Carlson.
The point is there are a lot of nasty people shaping minds in this world, and I'd rather the president fight back against white supremacy, not repeat and reinforce talking points about immigrant invasions (which he also gets from Carlson and Hannity).
So to sum it all up: Trump bears some blame but as Coovoo said he's just a symptom of American nationalism.