This is the fundamental problem with protecting a candidate whose entire base is really big on guns, big on having guns on them, big on using every inch of their already permissive rights, and no matter what, the candidate’s rally is a highly likely place for them to flex their pieces, even if they can only wave them around in the parking lot.
You can’t just do the obvious thing and put rounds in everyone you see with a rifle. White girls are going to be out in the parking lot doing influencer dances with AR-15s. The muzzle might wave in Trump’s direction while she boot scoots. We don’t know what kind of orders that sniper had, but probably something along the lines of “look all these fuckers are going to be strapped if they can be strapped, stay chilly on the trigger and think twice, take no shots without orders.”
By the time anybody acted like a clear threat, the bullets were already flying. So what if he had a rangefinder? That doesn’t count as a “pull trigger now” level threat, not with this crowd. What an absolute bastard of a thing to provide overwatch for, you know?