He needs to know all the rules and regulations

You realize the State Department has all this in file and in their many lawyers brains', don't you? Tillerson didn't fire everyone but himself there when he took over. He had teams of experts at his beck and call

needs to understand all the different countries customs and needs

Again, as Secretary of State all he has to do is pick up the phone and minutes later he's getting the most detailed up to date CIA fact checked synopsis about anything, anyone, any place.

You think the entire gov't just starts over again, all fresh and new, when a different person takes over the presidency? You're going about this argument all wrong. The points you think you are making are incorrect, and wildly blind to how governments operate.