You have a point because if we reason the whole situation of Palmer on the aspect you are talking about, leaving Manchester City was the best for him because Manchester City is like a club were all the players use to be very competitive among themselves in other to have more chances and noticeable to people, which would have affected the growth of Palmer because I realized that his sudden performance was when he left the club because during that time he was still playing there he was not this good probably because he is not always given much time to perform but since he joined Chelsea he has the time to display all the hidden performance he had, so actually your point is good.
Enzo Maresca is gradually unveiling the true color of Cole Palmer in Chelsea team. There are quite amazing qualities about this player, he's style is rare and he's currently the best player at the Bridge. Chelsea now have Cole Palmer as their main player, the potential talent under Pep Guardiola is doing a great job at Stamford Bridge. There's nobody like him in the Chelsea team, he's ambitious and knows how to enchanced his abilities. Sometimes it's advisable to push for the exits door of an elite club.
Cole Palmer was rare gem in Manchester City, nobody was able to spot the English talent out because there was heavy presence of main players, thereby depriving him the golden chance to exhibits his potentials. Manchester City have elite clubs to compete with and Pep Guardiola don't have that time to sort out his strategies or plans on using his substitutes. Palmer made good decision when he triggered his move to accept Chelsea bid, he's at his peak, not a one season wonder.