Cops aren’t trained in operational security. When you have a large event with multiple agencies and groups of people doing different things, then it’s easy to blend in if you act like you know what you’re doing. You can walk into almost any building if you throw on a high vis vest and carry a ladder. People will hold the door open for you and even let you into high security areas if you are smooth enough.
This kid obviously didn’t blend in if the cops were talking about him and taking photos.
Crazy person open carrying an AR 15 would probably blend in fine at a Trump rally…
My educated guess is that they looked at him milling about outside the rally and assumed he was a Trump supporter based on his look and wouldn’t be a problem.
As for the real answer, we’ll have to wait for them to give a statement, but it’ll likely be watered-down misinformation that paints police in the best light, so we’ll probably never know for sure.
A button-down shirt/khakis and lanyard with a name badge often works, too, especially if you’re talking while using a Bluetooth headset and typing on a phone. People just assume you’re some low-level exec or IT support personnel, esp if your phone is on one of those tacky belt clips.