That is right before Enzo Maresca joined Chelsea team did not play well and had trouble finding their rhythm. But after Maresca arrived he made it priority to make team attack and defense stronger by bringing in new players. As coach Maresca probably focused on most important things and maybe he thought that if defense was strong goalkeeper would not have to worry as much. I think you are right that it is not fair to blame just one person. Every successful team needs time to develop and Maresca has started that process successfully. Also it is likely that coach has plan to find better goalkeeper slowly which will help team play even better.
Enzo Maresca did bring a good impact to the blues, but I feel Mauricio Pochettino is still better than Enzo, Mauricio Pochettino he gave a positive impact and more opportunities were not given by the Chelsea owner and also the players given were not in accordance with the wishes of the leader, this was also felt by Enzo, but apart from that I also prefer Mauricio Pochettino with his experience and also his playing style is more readable and I see that currently under Enzo it has not gone well.
Enzo also had a hard time choosing a goalkeeper to play because what they had under the crossbar was indeed very unsatisfactory, therefore the first problem that arose was in their goal defense, facing Spurs in another London derby Chelsea had to show the desire for 3 other points because if they wanted to be in a good position then Spurs had to pass them, especially since Spurs were not in good condition.