Guardiola hasn't been sacked, but it is not only because he knows his worth, it is also because he is the best coach in the world in terms of influencing players and making them better. I doubt that Klopp would ever be sacked as he is very similar and both have their successes. They would rather leave a club in agreement with the clubs' bosses, but not get just fired I suppose. They are also different from Mourinho who likes to provoke everyone, including officials from his own clubs. He is more likely to get fired at the end of his engagements than to go just because he doesn't want to stay anymore.
Is it fashionable to fire coaches who win?
Spalletti won the Scudetto with Napoli, who left
Guardiola won the Champions League, do they want to send him away?
But has the world gone mad? I don't know, it seems crazy to me.
After all, if that really happened, then on what basis was Pep Guardiola sacked?
It makes absolutely no sense to sack Pep and also, Pep departure or move from Barcelona to Bayern Munich and then to Manchester City, it happened because of his own will and not because of the wishes of the club owner or boss you mean. Also about Spalletti, basically Spalletti wants to leave even though there has been an offer to extend the contract. So yeah, it doesn't really make sense for them to be fired because anyway, the reality is the club still wants him to stay, but they have their own choice to stay or leave.