>>280813729
>in favor of the Hashira aka side characters.
Elite group of good guys is a safe bet for franchising and merchandise, this has been proven since all the way back with the Gold Saints from Saint Seiya and their modern counterpart with the Gotei 13 from Bleach, their colorful designs are easy to make popular, and when they hit with audiences then the merchandise pool increase several fold as they are a group.
Tanjiro, Zenitsu, Inosuke and Nezuko had plenty of focus already, all very popular in their own right, the Pillars were the next step to expand the audience response.