I'm not a gun guy and I've been lazy (I only read the very short article) but to me it seems like a 10/10 "What the fuck were they thinking?" screw up by the Secret Service.
Sniper shot at former President Donald Trump from 130 yards away on roof of manufacturing plant
Yeah, so far as I can tell the only reason they get by is because everyone else is every bit as generally kind of naive and gormless