Chelsea could have kept Tuchel in the team but decide to make a critical change like that when the league is in full swing? Why create a problem when there wasn't one in the first place.
The second Tuchel was fired, Chelsea's team became disorganized. Chelsea was unable to find a solution to a host of issues brought on by a critical change they made since they believed that a new coach would be the key to winning the premier league or champions league trophy.
If Chelsea's owner had realized the money spent on bringing in two different coaches who didn't perform as planned to replace Tuchel, he might have chosen to give Tuchel more time to lead Chelsea rather than dismissing him abruptly after Chelsea's first champions league defeat of the season. Chelsea owner fervently believes that Chelsea will succeed if he signs his old-time friend coach "Potter" as Chelsea coach. That mistake alone caused problems for Chelsea's football club.