I think the consensus is that Marvel is run by people who have such a low opinion of the Black Panther IP and of black readers in general that they’ll allow any black person, even those without experience in fiction like Coates, to do whatever they want with the franchise. As long as it’s a black writer and black people in the stories the standards are much lower than they are for a white-led book like Thor. Then there’s a contingent of black readers who actively support and attack those who recognize the low standards to which Black Panther is being held or who straight up think the book is obligated to highlight all black heroes at the expense of the title character.
Marvel doesn’t have any higher ups genuinely interested in fostering any sense of stability with the Black Panther comics, hence why Coates has been allowed to run the title into the ground along with equally garbage BP writers on the spin-off books, with Marvel reaping the benefits through good PR despite putting out low quality books with black leads. But given the commercial failure of this run and the vast majority of the spin-offs we’ll see if Marvel continues in this direction when they inevitably relaunch the book later this year. My hope is we get David Walker or Saladin Ahmed, since unfortunately Marvel has allowed up and coming creator Geoffrey Thorne (writer of the BP KIB tie-in) to go to DC instead of letting him write the solo.