The 'good players go shit for larks' theory is not one that I have any time for.
I respect them all as professionals. However, they are all intermittently affected by varying levels of confidence, form and motivation. You know, just like all human beings are.
It is the managers job to maintain the highest level of performance possible from each individual. They do this with their interpersonal skills, their tactical and motivational abilities, and their command of a collective drive to achieve a shared goal.
Very few managers are good at all of the above. Very few can even sustain periods of being good at most of the above. That's because most managers are pretty terrible at their jobs.
Two years ago, we saw what is possible when a manager gets it all just right. However, Ranieri had never really done it before or since. Shakespeare was never going to achieve it because he hasn't even got the basic skills to be a manager.
Puel has only shown any aptitude for having a coherent tactical approach. It's a stupid one that is doomed to fail but he does have one. In every other important respect, he's completely hopeless.