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If you check the situation very well you will understand that everything is just all about money. If a club has a lot of money, it will be able to buy any kind of coach they want and as well as by quality players to enable them win trophies. But if a club is in financial problems, they will likely not be able to buy any good players or sign good coach and as well they will remain in their financial problem because they will not win trophies that comes with monetary reward.
And that very much you were referring to, PSG had more quality than Barcelona because they were more financially stable and that was why they want and added a whooping $50 million dollars to their portfolio. So dismissing Xavi Hernandez and not serving the financial crisis will not bring any positive results to Barcelona in order to content with Real Madrid this season.
Having quality players and coaches really supports the team's plans to win the title at the end of the season. I agree that financially strong teams like Real Madrid, Manchester City and PSG tend to dominate their domestic competitions, but in European competition like the Champions League that is never guaranteed.
We certainly have proof of the assumption above and the three teams I mentioned both won the domestic title. Real Madrid has a lot of money to buy star players, which makes them superior in squad depth compared to other rivals. The same thing must be acknowledged by PSG and Manchester City, so I never wonder why they can dominate.