Because Trump wanted to have been shot, not hit with a shard of glass, in a location likely above the ear.

But, tiny shard of glass doesn’t play well with the base.

The real cut was likely sealed with medical adhesive the second Trump was in the car. That too wouldn’t play well, so he got a medic to slap a bandage on the side of his head, but he took it off because his dumbass followers were wearing ear diapers as well.