A conspiracy is all but certain in the JFK case. But some kind of black tie event where all the top men - including prominent personages - show up with lawn chairs and buy some peanuts and a hot dog to snack on during the show tends to stretch credulity way past the breaking point.
The “top men” did not show up—but many “mechanics” did.
One anecdote with dozens of witnesses:
In the seconds after the assassination many folks rushed towards where they believed the shots came from (the grassy knoll).
They were greeted by well dressed men who showed their secret service identification and told them that the situation was under control.
What makes this story most interesting is that there were no secret service agents on the Grassy Knoll during the assassination.
The “secret service” agents were imposters.