Good faithed questions: should they have just forcibly rammed his head back down when he repeatedly stood up in defiance? Does Trump have zero responsibility for potentially putting himself at further risk by deliberately going against their actions and standing up to face the crowd in order to do his gestures?
The shooting never should have happened, yes. But he also defied the protocol during such a situation and put himself, and perhaps those agents, at further risk. That is on him, not them.
Different risk:
The SS risked his life and others by the complete failure of duty.
When a person is in shock from a bullet they can’t be responsible for the risk of their movements. None of us can predict what we are going to do in various situations. There was 5 or 6 of them against 1. Forget about the shoes no matter who it is. Trump was obviously in shock by asking for his shoes. Who needs their shoes when you have just been shot and on the way to the hospital?
I unexpectedly went into labour, water broke and had the baby 30 minutes after I arrived at the hospital. Total surprise, a month early. I was screaming for my lip balm when I was leaving my house. I was literally trying to stop the door from closing so someone could get it. I laughed about it after when I was no longer in shock.