I used to feel that if a club had world-class players, any coach could manage that club and get good results because the players knew what to do on the pitch to win a game, but after I had seen how different coaches had failed to get good results in clubs that had world-class players, I agreed with you that getting a good manager is very important for a club that has world-class players to flourish and win matches easily.
To succeed, a club need to have both world class players and outstanding head coach to manage their squad well and go through many competitions till the ends with titles. If you only have good players but don't have a world class head coach, it's hard to succeed with titles. The same with situation if you only have a world class head coach but not enough good players, your team will less likely win titles.
If you have a good head coach, you must provide him enough good players to cook from training to matches and win titles together. It's big and very important condition at any club and it has been proven in football history at both club and national team levels.