Did the Secret Service Advance Team do a thorough sweep of what I heard called “The AGR Building?” One attendee said that building was several hundred feet away.
What makes you think they didn’t want this to happen? Don’t trust anyone in government...
Sniper on top of a building outside of the venue.
There is an interview online of a man who saw him scaling the building with a rifle and who tried to get the attention of the local police and/or secret service, but was ignored.