Can thank Houllier for that. I think after 98 the football syllabus is set in stone for life. The interesting thing is before Clairefontaine opened in typical French fashion it took them like 8 years to make the decision to go ahead with the academy and it took winning in 84 to actually sign off on it.
Another interesting thing about French football is all of their big name players have either born elsewhere or been sons/grandsons of immigrants. Kopa (Polish) Fontaine (Born in Morocco Spanish mother French father) Platini (Italian) Tigana (born in Mali) Luis Fernandez (born in Spain). The Djorkaeffs (Mongolian/Polish). Everyone knows the squads from 96 onwards. Even Cantona is from Spanish and Italian background.
The only French French player I can think of is JP Papin.
The 90s area was definitively the moment when the French Federation decided to professionalize and centralize the sport. We historically had a strong public education system in France and the federation used this philosophy for football as well. Which means you end up with a formation open to everybody regardless of their background, including non-citizen, and FREE. Some argue that this is prime meritocracy.
This is why: 1/ The French league became basically the best youth development league and produced mad talents for other leagues and countries. 2/ Other EU countries started to copy this system in the mid 2000s. 3/ The negative consequence is that it's hard to keep the talent home and it favors a business model where local academies rely too much on richer foreign clubs.
Regarding the "diverse" aspect of the squad, it simply reflects the immigration waves in France. Anglo American media have been recently obsessed with the number of Black and Muslim in our team but it's not a new thing. People started immigrating to France in the late 1800s... Eastern europeans after WW1, then Southern Europeans, then Maghreb and Caribbean, then West Af in the 70s/80s, Central Af in the 90s/2000s. These waves were composed of mainly poor and low educated individuals, which means school success is less likely for their offsprings. So sport, not just football, is seen as a great opportunity to move faster in the social order. But it's a riskier option too.