I have trouble dismissing all the circumstances myself, however I always try to practice questioning my assumptions.
One thing I've been realizing in this is the (well known) effect on security when you surround yourself with loyalists. There's video of people shouting at police/USSS and the response seemed to be one of distraction.
That's because all the police are loyalists, and all the USSS Trump keeps are too. And what are loyalists doing at a Trump rally while Trump speaks? Watching Trump. Not rooftops. Further they're going to be Yes Men. If they're taking too long and get hurried by the higher up, they might listen instead of doing the right thing and saying "no, we need to follow protocol".
That some kid took a shot at Trump isn't terribly surprising to me, even if he's a Republican. I can think of a hundred reasons why it might happen without the need to tie in world despots and geopolitics. The very notion that the kid might affect geopolitics is motive enough for certain kinds of people we might expect in tumultuous political times. Republican and Democrat voters share at least one common thing, neither group is completely and totally represented by the party they vote for. There's lots of room for dissent in the ranks on both sides. We just only often see one side of it in the media as of late.
I'm not saying any one story here is true or false, just saying there's considerations I'm making that I'm not seeing discussed elsewhere.