Coates didn't ignore Hickman's ending... he didn't know it when he wrote his story. FOrtunately (or unfortuantely depending on how you look at it), he really didn't need to know Hickmans ending because marvel essentially decided to just ignore it and say all the incursion happened anyways. So Hickman traveling back to New Avengers 1 really ended up not doing anything.
THe notion at the end of Secret Wars was that T'CHalla traveled back in time to New Avengers 1 before all the bad stuff happened.
But marvel decided that the incursions all still happened, so effectively T'Challa traveling back in time didn't change anything. Wakanda was still attacked. Shuri was still killed.
Hickman helped me break the cycle of buying BP for completion purposes as opposed to pure enjoyment. Although I came close, I resisted the urge to waste not a single red cent on Coates.
I made better use of my disposable funds supporting single mothers & college women at the strip club.
Coates had no interest in what Hickman was doing or else he would have inquired. We have Wakanda launching an international space program in Ultimates and we have a government to feeble to stop a rebellion or too sorry to do anything about rape camps springing up like weeds all over Wakanda in the BP solo.
I didn't say he ALWAYS gets darker tones. I merely said he'll always get his share of that. Overally I don't think Hudlins run was that dark either. Then again Hudlin did kill off the majority of T'CHalla male supporting cast and ended his run with the character dethroned and just recovering from a coma. So even he went there eventually.
But you're right, most of his run had more of a Saturday MOrning Cartoon vibe, and I mean that in a good way. It's probably a big part of why it sold as well as it did.
It SHOULD be. We know the attacks still happened, but Wakanda is in better shape than it was in Time Runs Out and there seems to be more than 2000 Wakandans left. Either the second time around the attack wasn't as bad, or maybe Reed and company magically helped Wakanda out when they restored the multiverse. But yeah... there's a lot of question marks there.
According to Starlin he tried inquiring what HIckman was doing with Thanos when he was doing his Infinity stuff, and had the same problem.
But like I said, because marvel editorial made the decision that the incursions still happened (rather than retconning the entire MU all the way back to NA 1), it really ended up not mattering whether or not he knew Hickmans ending. Marvel essentially ignored it anyways.