The rise of a player depends on different variables, team spirit, players confidence ad the coaches confidence. We can uses instances of players like Romelu Lukaku, Alexis Sanchez , Mohammed Salah, Victor Moses , Jordan Sancho, Kevin De Bruyne, Bukayo Saka to mention but a few.

These are players that played for their former clubs and were deemed not good enough to play for the clubs , some were loaned out and eventually sold off while some were restricted to bench roles and eventually forced their ways out of their parent clubs and some have so far enjoyed the confidence their coaches put on them and are repaying with outstanding performances week in and week out.

Seeing those players in their new clubs now beg to ask the question, what was wrong at their former clubs... was there no team support, did the coach lack confidence in their player, or did the player feel he wasn't good enough.

We've seen cases of coaches openly criticizing their players and it actually kills the players morale cause he feels nothing he does is good enough to please the coach and repose that confidence in him.
And when is player is low on morale it affects his game.

At the end all factors come into play, the coaches confidence helps a players morale to grow and help the player be a better person. Once one of these three factors are missing its shows in the players output.