The US Secret Service had said a few days ago that for some reason, no-one knows, there was no counter-sniper put on the very roof where the shooter Crooks took up position. It was a site supposedly outside of the field of operation. However, there is now a video circulating, see link below, showing the shooter Crooks, walking around on the roof top in plain sight. Sight plain enough for the footage to be filmed. So, why did the Secret Service not see him? Of course they did see him, and the plan was to let him take a shot at Trump. This is the one hypothesis which accounts for all the facts, not ten thousand mistakes.
https://vigilantfox.news/p/it-only-took-one-day-to-debunk-this