IIRC the consensus was the secret service agent tackle caused it. Not surprising for a frail old man to be scraped pretty easily. The pageantry with the gauze was to leverage the injury into a tough guy image instead of sad bruised geriatric.

I don't really buy the staged conspiracy theories.

• Secret service protection is reduced when you're not the president and would be spread thinnest during peak rally-season
• Trump's polling was really, really bad at the time. The motive makes sense along with the demographics of the shooter (all these assassination attempts are from disillusioned groyper-types)
• He looked confused/in shock during and afterwards and he's not a good enough actor to fake that
• A person died from the shots, no chance live ammo would be allowed
• In the weeks following Trump made very few appearances and rumors were describing ptsd symptoms. If it were staged you can be damn sure that blowhard would be putting on photo shoots every day