I know this is difficult to grasp without field experience. Things take longer time than anticipated even if the operatives are well trained and experienced.
Thank you for confirming I did understand what you had said.
I just want to make sure I have all this information correct.
1. The guy on the roof was spotted 30 minutes before he shot Trump.
2. Witnesses took pictures and notified the police.
3. The police also saw him on the roof.
4. In the building where the man who shot Trump from the roof were Secret Service agents who had seen this twenty year old man use a range finder to get the distance to Trump before he went up onto the roof.
5. A sniper there to protect Trump had the assassin in his sights for three minutes but was not permitted to shoot him.
6. Meanwhile during all this time no one thought to get Trump off the stage.
7. Finally a day later when asked if he had talked to the director of the Secret Service Biden said "yes, I have talked to him" (the director is a woman).
Meanwhile
@Nehemiah6 is saying we cannot make jokes about this and
@Susanna is saying it was probably just the result of a lone wolf and human error.