While there’s some element of truth to what you’ve said- the DNC is using the “End of Democracy” meme as one of their primary themes in their campaign messaging- I don’t think that had anything to do with this shooting.

Statistically speaking the vast majority of domestic terrorism comes from far-right extremists. We don’t know the motivations behind the shooter at this point in time, but the consensus seems to be so far that he was conservative.

I think it’s much more likely he was radicalized online and either

a) wanted to kill Trump to further polarize the political tension in an accelerationist sense (sort of like how far-right organizations were shooting both protestors & police during Euromaidan. Just to increase the outrage, the violence, etc).

Basically an attempt to weaken the regime

Or

b) he became a white supremacist and those tend to hate Trump. Go on stormfront forums and see what they say about Trump. They think he’s a jewlover, fake messiah, etc. They hate Jews, Trump loves jews. Therefore, Trump is a potential target.

Or

c) was just nutty plain and simple. Ie killing Trump would unite him with some cartoon character from Nickelodean in the afterlife.

All of those are vastly more likely than someone being radicalized by DNC messaging, I believe.