I don't see Enzo Maresca has being the main reason for this improvement even before he came, towards the ending of the season under Poch we notice improvements and there are tactical decisions he has made that makes me sound like this TBH.
Now we are back at the Champions League, let's see how we compete against the big boys and improve to dominate here again and possibly lifting another Champions League trophy.
In my opinion, Enzo Maresca is the main reason Chelsea achieved a good position in the Premier League, managed to win European competitions, and reached the Club World Cup final. He is managing to organize Chelsea well, which had been lost for many seasons ago. This is probably due to having many different coaches
each of whom made his own signings. Mourinho is a coach who, when he arrives at a club, organizes it his way, and when he leaves, he stays there. It is very difficult for other coaches to organize the team. Enzo Maresca is ensuring that Chelsea has a squad composed of a strong A and B team, so that even in the event of injuries, the team does not fall.