To be fair, after having so many titles, even going for a treble one season, I feel like Pep probably deserves enough credit to wait for a while before we decide to pull the plug on him and call him a bad coach or anything. I also understand, there are too many fans of other teams all out there who hated Pep for getting success while their team couldn't, there are so many teams that spent way more than Pep did, and still called it a bought success, so I understand why people would hate him, and that is why they are so quick to jump the trigger to call him bad. But in reality, dude is good and he proved it, he won enough to say he is great, and I am sure we can give him some more time to recover from this.
That's a good enough explanation for the mood of the Man City fans and it's probably a much easier one to say. The era of success is different and it's going to be replaced because it's impossible for one team to dominate all the time. Pep Guardiola has given everything for Manchester City and now he's got a problem that could see him out of Manchester City. It is natural for people to say that and even Manchester City fans themselves express different feelings when their favorite team is in decline like now. Football is like this because it is impossible for a team to maintain great success for every season and maybe only Real Madrid is the only team that can prove that, but in some capacity they also lost the opportunity to perform better.