It is hard to believe, indeed absurd, that a supposed elite security force would allow this to happen, that their standards could be allowed to slip so much. But it's even harder to believe that half of the team are in on some plot, and are willing to put their unknowing colleagues and civilians at risk. It's harder to believe the deep state or CIA or whoever would recruit someone who can't shoot to shoot a former president protected by an armed security team including snipers. It's harder to believe that he didn't really get shot and he's acting hurt while one of his supporters bleeds to death. It's harder to believe the whole thing was staged.
It's an unlikely event, however you look at it. Complacency seems to me the least absurd, even if it remains somewhat absurd.