What's crazy is that this guy had no reasonable expectation of actually being able to pull this off. First, he had to walk from his car with a very conspicuous gun in his hand. Then he had to cross a wide open area with this gun in his hand. Then he had to climb a ladder and access a roof, one which would reasonably be covered by SS marksmen. Then he had to position himself in a way that gave himself a view of trump, all while people watched.
Somehow no one outside a lone police officer reacted fast enough, and even then he either wasn't able, or wasn't willing to engage.
Basically, every single thing had to have gone right, and it did. Of course, for all of that to happen, there had to be staggering failures along the way. It's just insane.