Where is the evidence?
Yes, let's kill the President in broad daylight in front of hundreds of people - many with cameras - and use multiple shooters located all over the place.
This makes no sense at all, of course.
These are very powerful conspirators with lots of resources. So they decided to use the most convoluted, complex plan possible.
Hey, it's fun being a conspiracy advocate. You can make up all kinds of imaginative things. Double agents, and spies, and world war and secret this and secret that.
Gary Mack recognized much of this conspiracy mongering before he died and changed his views. Yes, he was a conspiracy believer - he thought Oswald had help. But he was smart enough and open minded enough to realize that most of what the conspiracy people like Simpich and Peter Scott argue is just nonsense. But fun nonsense.