I don't agree with what you say. In my opinion Garcia made too many changes all at once at the beginning of the championship and it would have been better to take advantage of a proven team, which had won the previous championship many weeks before it ended (and this explains the decline towards the end of the championship when they had many points advantage over their direct competitors and therefore had an understandable drop in tension), and making small changes and modifications to the formation and game organization during construction and based on the form of its players.
I agree with most of your post, but I also think that sometimes as outsiders it is easy for us to have opinions. I actually have the same opinion like you, but we have to admit that we don't see the team at training sessions. Signaling to the team that the first eleven is set in stone because of what they achieved last season isn't necessarily the right path of action for a new manager. If it works out when he changes a lot, then he is the hero but if it doesn't he will immediately have to deal with repercussions from the public, the fans and perhaps the team itself. It's often a fine line for new managers and really, a manager taking over a team that just won the title with 16 points ahead of the 2nd can essentially only lose. What is left there for Garcia to win?