Belgian education was in French, as was its high society. For a time, French speaking people from Belgium wanted to become part of France. Many at this time moved into France, which is why along the French border there are many Flemish words used in the French language. It is only more recently that Flemish is seen as on par with French in Belgium.
From 1940 to 1944 while Belgium was under German occupation, the Nazis tried to use Flemish as a way to divide the nation.
In 2009 Dutch dictionaries published two versions of Dutch (Belgian and Netherlands Dutch) and regarded both as equally acceptable.