> Less than 140 yards and missed?

Person aimed for the head, seems like he wasn't trained how to kill people.

Anyway, the person knew they would die seconds later, heavy breathing makes it is massively harder to aim when you are nervous, then it is easy to hit a moving head at 140 yards.

Presumably Trump would have a vest on

Rifle rounds go straight through medium vests, you need a really heavy and bulky vest to stop them, Trump wouldn't wear one of those. The typical vests you see just stop low caliber bullets like pistols, and then you hope secret service can stop anyone with a rifle from getting a shot.

The times I’ve worn vests I’ve had to have ceramic plates in for ak-47 style bullets, but I’d assume that the secret service would have something more fancy available.

Nope. Thick layered ceramics are still pretty much the best stuff to stop high energy rounds. Got 2 sets of AR500 plates myself.

There is actually now very expensive cutting edge stuff (FRAS) that’s flexible and can barely stop a 5.56 round, and i’d assume important people have whatever top secret upgrade exists for that, but that could be wrong.

Difficult to practice with your head full of adrenaline.

The practice is there to help when your head's full of adrenaline.

That's fair, but it's only part of it. The issue of "stage fright" still exists and can't be mastered just by practicing your craft to proficiency in solitude. There are other practices, like literally going on stages (speaking, performing) and becoming used to the pressure, that would overlap.

Hopefully I'm not giving useful tips to future assassins. :P