One point to bring up as I don't think I have seen it yet. When team X hires a crew chief after firing one, does team X expect the new crew chief to run the car with all the componets that the previous CC didn't have success with ?
Like blowers , pistons, cams , injectors, clutches, etc. Throw chassis in there too. If a new CC has a blank check to start off with all that he is used to running and succeeding with , then I would expect results sooner than later.
On the other hand if the new CC has to make due with the parts on hand, it can throw the odds of success further out of reach.
The one thing I seem to notice that works is when the team is directed and tuned by ONE person, not a small committee.
I seem to remember reading an article about the F1 Ferrari team. In the front office entrance to the shop reads a sign,
" This Team is run as a dictatorship, if you are looking for democracy it's not here "