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.
Honestly, if Chelsea's owner had been patient enough with Pochettino, Chelsea's performance might have improved significantly based on the improvements we witnessed towards the end of the season. I did not really expect that Pochettino should be sacked last season given his performance. Pochettino made Chelsea recover their performances, despite it not being as expected. Let's see what the new manager will do; maybe Chelsea's performances will improve as we expect next season.For now, I can't really say that the new head coach will be better than Pochettino, but if Chelsea's performance does not improve as much as fans expect, it will be regrettable to have sacked Pochettino. I just hope the new manager performs better than Pochettino.
Logically, Pochettino deserves a chance to stay for another season. He brought Chelsea to 6th place. This was a big achievement, as they finished 12th under Lampard previously. The decision to sack Pochettino is the worst ever i seen. Pochettino had given his best last season for Chelsea. And it was his first season with a young, inexperienced squad after a major overhaul of the club. Boehly once again did it wrong by firing Pochettino from his position as head coach.
About Chelsea's performance, I'm not sure they will improve. No improvement so far has been shown by Chelsea in the pre-season games. Pochettino did better in the pre-season games compared to Maresca.
That's why fans have asked Todd Boehly to message Lampard. Fans are expecting Todd boehly to sack Maresca in the middle of the season. Fans are not having big expectation to the Maresca.