Like how you explained it Mind of Shadow. I would add that Coates also benefited from interest in the Black Panther film, and it being Black Panther's 50th anniversary didn't hurt either.
Years and Years gap between solos, 4-5 years of Hickman building the character, Stelfreeze art with Stelfreeze covers, black panther film, 50th anniversary, multiple marketing gimmicks, using the Atlantic and YT and Twitter to market, having actual BP merchandise in every store with ease, BP in cartoons again, BP in team books again (ultimates), BP allowed to have spin off books
Priest and Hudlin sold what they did with NOTHING handed to them on a silver platter like Coates did.