But the book was about M'Baku. They never pretended otherwise.
Indeed the book was about M'Baku and as advertised a new hero was to be introduced. What we got was a supporting character trying to carry a story beyond his weight class, thus the need for so many other characters to help redistribute said weight. The book could have been about M'Baku without having T'Challa give him regency for that matter.
They didn't even put 'Black Panther' as part of the title like they usually do.
While they did not put 'Black Panther' as part of the title they certainly did use his picture front and center relegating M'Baku's picture to a variant cover.
So if he looks better than thats what should be expected.
That just it, he didn't look better or more interesting, he was just there.
I would expect M'Baku to treat Tchalla like a normal person. He knew him for years as just a comrade as part of the Maroons and he has a distaste for rulers the same as he does for Vibranium.
But the fact is T'Challa is not a normal person. T'Challa has been a king for many years. He is a just ruler who does not give offense but does not tolerate disrespect.


Even with all of that, M'bakus' last lines of the book give Tchalla most of the credit.
If you are referring to the last line written in black boxes, that's T'Challa speaking.