We don't know that they didn't. I am very sure Trump himself has spoken to those on his detail as to what they had heard, what they knew, what they saw. The media and/or conspiracy theorists and pure propaganda manufacturers on social media cannot be trusted to get it right. Too often they just make it up as they go along.I can see what you're getting at but if they weren't in on it then why didn't they listen to the police and rally attendees.
And Trump is also very aware and grateful to his detail who put their own bodies between him and bullets that were still being fired before a Secret Service agent got a clear shot at Crooks and took him out with a shot to the head.
Bottom line I don't know what the whole story is and neither does anybody else apparently who weren't directly involved. Maybe there is a more sinister plot here and that should not be dismissed. But neither should we buy into and repeat internet theories and chatter when we don't know for certain exactly what happened.