I'm starting to think this decision was based on the fact that they think T'Challa being BP is not necessary as the focus was more on Wakanda and not a lot on the character of T'Challa which is what I was expecting to be expanded upon in the sequel. But Disney just went "Hey T'Challa being BP is not necessary, why focus on this hero when the world he is based upon is more interesting?". I mean if you look at the recent BP comics, there is more emphasis on the world of Wakanda and the supporting characters than T'Challa himself. This unfortunate tragedy has just propelled them to take this route.