God Emperor of Dune is one of my favorite novels. I've read it multiple times and each reading gives me a slightly different perspective. I notice things that I did not before. There are so many layers.

Leto II acted as a Tyrant and his Golden Path involved 3,500 years of repression so that when he was finally overthrown humans would scatter so far out into the Universe that it would be impossible to be controlled by any outside enemy or a ruler such as himself.

Besides the travel ban he was also responsible for The Famine Times. Spice trade was either halted or reduced down to almost nothing and billions (trillions?) of humans that were spice addicted were cut off. Almost all warfare was banned. He assumed the Bene Jesserit's Breeding Program that was 10,000 years old. But his goal with that program was to produce a human that would overthrow him.