Mauricio Pochettino got fired because he failed to meet up, it was a harsh decision from the Club's owner, Todd Boehly.
I think it is reasonable that Mauricio Pochettino has not been able to fulfill his promise because Chelsea did experience a serious decline in the previous season and the coach also needs time to be able to fulfill what is expected and since the time he took office as Chelsea coach he has improved Chelsea's performance and managed to finish better than the previous season, even though his contract at that time lasted 2 years if Todd Boehly had been more patient, Chelsea could have been in the top 3 in his second season, unfortunately the club was not that patient and they fired Pochettino at the end of the season.
Mauricio Pochettino cannot get Chelsea out of the slump in just one season, he needs at least two seasons to achieve the desired results. Jurgen Klopp also needed time to bring Liverpool out of the slump, but because Klopp had the trust of the management, he managed to make Liverpool win several trophies. Chelsea dismissal of Pochettino was too quick, Todd Boehly was too ambitious to improve Chelsea performance without going through the process, clearly that cannot be realized by any coach. If Todd Boehly doesn't change his attitude soon, Enzo Maresca will also suffer the same fate as Pochettino because he will never be able to complete his task in just one season.