Here's the thing... Coates went BIG on it.
Yes, Hickmans run alluded to Wakandan space exploration but that didn't necessarily mean we would have an entire galactic empire up and running a few years later. If Coates wasn't particularly in favor of taking the story in this direction he could have made this MUCH smaller. A space colony and a few stories here and there in space frankly would have been more believable. In Star Trek it took earth centirues to become the Federation we are familiar with. Coates is having T'CHalla pull that off in a small handful of years by creating a freaking empire.
For him to go this big I think implies that he has to be willing to really run with this idea, because it essentially is changing the course of the entire mythos from here. It's no longer a story about a hero ruling a small albeit advanced african nation... it's now a story about a character running a galactic empire. That's a huge shift in direction that will effect not only the rest of his run, but frankly every BP run afterwards (assuming this all sticks).