Croatia also mainly Croatian ... why is Croatia so good at soccer? Because everybody there has the itch to play.
(Modric, Stankovic, etc etc)
Just a more general comment, the European countries with multiple African players didn’t necessarily recruit them from Africa, they came to play in European soccer leagues as young talents or they are second generation. At the same time, some still play for their African homelands such as Senegal who were at this World Cup and did fairly well.
Japan and South Korea, also Australia, looked to be mostly “old stock” players, Canada on the other hand mostly an immigrant team. Mexico another team without much “diversity” although scoring very well on the Hispanic index ;)
Only whitey can do wrong.
If someone asked me “Do you want to live in Nice FRA or Lagos NGA?” it would be an easy answer.