What makes a team strong?

Why do do some teams loose form by just selling a key player?

Eg: Liverpool - Suarez

Why do some teams get stronger when they sell key players?

Eg: Chelsea - Mata

Why do some managers do a complete/partial team overhaul and the team grows stronger?

Eg: Southampton - Ronald Koeman

Why do some managers do a complete/partial team overhaul and the team achieves little or no success?

Eg: Manchester United - Luis Van Gaal

Why do some clubs acquire players for so much and the player turns out a flop?

Eg: Manchester City - Mangala, Chelsea - Torres

Why do some players cost so little but yet perform excellently?

Eg: Tottenham - Bale
......


That's all I can recall right now. It's quit confusing how these teams perform. I don't want to believe managers does the main work in teams. Although selection has a major factor in teams but if a player fails to perform well, it is then blamed on the manager.

Football lovers please explain..

bale was a left back wen he went to Tottenham. he wasn't spectacular until he switched wing..

patmaine:
bale was a left back wen he went to Tottenham. he wasn't spectacular until he switched wing..

But he did perform well at Spurs right?

What is noe happening to him at Madrid?