No. MMA goes through cycles where different styles work in different divisions. It isn't uncommon to have a number of fighters with similar backgrounds all winning titles. By the way, there are four BJJ blackbelts holding belts right now (JDS, Silva, St. Pierre, and Aldo), five if you count Barao... so... not really a substantive difference.
Demetrious Johnson, Dominic Cruz, Benson Henderson, GSP and Jon Jones are all wrestlers and dominant champions. Is it safe to say that wrestling is the # 1 fighting style on which to build a base as a true champion?