why French became the dominant language socially speaking in Belgium
Has nothing to do with it. It was the Bourgeoisie responsible for this. Back in the day when Flemmish mayors spoke French in order to administrate their towns. The Flemmish Bourgeoisie spoke French to distinct them from the common men and to classify them as elite.
It was widely accepted that French was the language of the rich and Flemmish the language of the poor.
Edited 3/21/2016 14:09:35