The bomb sender's van had photos of Hillary Clinton with a target on her face. I'm sure you've heard the "Lock Her Up" chants at Trump's rallies. When the political rhetorical speech comes out of the mouth of the leader of the free world ("Body slam him". "Punch him in the face and I'll pay your legal fees") then it kind of gives these unstable folks the extra push they need - it's okay to hate "The Other" - to go out and commit these terrible acts.

And the irony of the president and the republicans in congress. They went completely crazy about Hillary and the server (see "Lock her Up") but radio silence when we find out that Trump uses an non-secure phone which the Chinese are listening in on.