Answer:
We were actually colonised by both the british and the french...but before our independence(1968) we were under british reign...
but then there are a huge number of mauritians who are from french descendent in mauritian(they are called the franco-mauritians and some of them are really rich because their families have been involved in the Sugar industry-used to be our biggest industry before tourism!) so yeah i guess maybe that's how we became french-creole speaking country.