According to Breaking Points, text messages from local law enforcement show they were aware and tracking the shooter and knew he was carrying a rangefinder, up to 1.5hrs before he shot Trump.
Local police photographed the suspect and suggested notifying SS Snipers to "look out" and sending in someone to "check it out".
The Secret Service and those up in the chain of command appear to have ignored the warnings and their requests.
Video here: https://youtu.be/6VIAGBfnNvQ
That's my running theory as well. It seems like incompetence from the top down, and it very likely could be.
But also it appears that ever lever you could possibly pull to fuck this all up was pulled. Every single time a single instance of someone trying to do the right thing was ignored, or intentionally made worse by doing the opposite of what was necessary.
Bottom line: the guy had a range finder and a rifle and was within shooting range of a former president. He shouldn't have been able to sit around on a roof top for an hour and a half to take aim.
That's why I don't think it was total retardation, just enough somewhere in the hierarchy to believe Trump's death would benefit them. There didn't need to be a plan (it's not off the table, but it's unnecessary), they just needed everyone in the right place to be on the same page. These agents knew there were powers above them that wanted Trump dead, and all they had to do was ignore one little detail that they could pass off as ignorance or a procedural mishap.
I don't think they were answering to the highest powers, to be clear. The existence of Trump scared libs into absolute compliance. Trump can't be their boogeyman if he's dead, and his death probably would have started more fires than they'd want to put out. The real powers, if they have any sense at all, want Trump to be alive, but impotent. That's the only way he's useful to them. Some fucking midwit lib running the SS though? Absolutely smart enough to put this in motion, and stupid enough to think it was a good idea.