After the JFK assassination the Secret Service became fanatical about controlling all the high ground and sniper prevention tactics.
Nowadays both drones and deploying of personnel and other portable surveillance technology makes it a lot easier to fulfill that mission.
That is why it is a virtual certainty that at least some SS supervisors and/or team leaders were part of the plot.
If it looks like a duck, walks like a duck, and quacks like a duck, it ain’t a cat.