~~~
For example, s good player will improve his performance if he is playing in England. While the same player will probably stagnate if he plays football in some minor league.
From what I can see, the current trend (a very recent one, I'd say) is for European players to get contracts with less known leagues around the world (one example is that of Cristiano Ronaldo playing for Al Nassr), and at the same time players from AFC and CAF participating in the top leagues such as Serie A and the English Premier League. European leagues always had Asian and African players to a certain degree. But this trend has really accelerated during the last few years, which is helping the Asian and African national teams in a big way.
That is not a new trend. It is very standard for players who are at the end of their career and want to make big money for a last time. Just see how many players went to China or Japan when they didn't have salary caps. Iniesta plays for Vissel Kobe or Hulk played for Shanghai. Xavi played for al-Sadd for even four years. Nothing new about it and not to forget how many stars went to the MLS. Ibrahimovic, Henry etc. It is all about the money.