Well I have noticed too, Bicorine in live usually fails hard to reach the perfection in execution of other soloists unlike Sarah, and for Werra historically Werra had always had a great relationship with influent journalist unilke JB who was acting like a star which made the journalist chose to push Werra instead of JB.
Werra knew since the beginning he wasn't a great singer this is why he built is fortune on atalakus like Bill and Celeo, Brigade and by letting singers like Ferre and so on to sing.
Promotion it is not a concept of being good but being smart pushing yourself, Deplick is better than Robinio and Fabregas at singing but he rarely produces something as big as Mascara or Tsha Nanu Boye, JB is one of the best if not the best singer of his generation but his album is there waiting while Werra already did three