The owners of Chelsea are not having any patience, they want results because they have spend too much money on the club but they are not seeing their money being used very well to better Chelsea as a football club. Pochettino would not have taken Chelsea to the level the owners of Chelsea want to see Chelsea playing at. There is no time to give the coach that chance to build up the team slowly, they want a fast response and for Chelsea to be playing with the top clubs. The sacking of pochettino is not going to be a regret by the board because he is not the right man for the job in spite of how well Chelsea were playing at the end of the season but by then it was already late because he did not start strong when the fans and everybody were expecting him to use his experience to make the players play good football.
But the fact is that no team can be strong in just one season. The Chelsea owner is really impatient, I remember the dismissals in the Abramovich era and in the Todd era were very different. The dismissal of coaches in the Roman era was indeed due to the coach's performance declining, whereas in the Todd era it was not due to a decrease or increase in the performance of the coach who had built chemistry with his players, but because of the business which was said to be long term, Pochettino was finally fired.
I also want to compare with other teams like Man United, Erik Ten Hag has been coaching Man United for two years, he was also given all the players he wanted in all positions, but instead of being good he got worse, even ranked 8th, the club's worst ranking ever. EPL history but still maintained. . On the other hand, Pochettino has only been training for 1 year, almost all of the players are new and young. Pochettino didn't even participate in recruiting players, the start of the season was ruined but at the end of the season he started to see a little progress but instead he was fired because Pochettino wanted to participate in recruiting players. Pochettino's dismissal was honestly very unfortunate at a time when Chelsea was starting to improve because there was already chemistry between the players. Firing Pochettino is not a guarantee that Chelsea will be better next season.