I was really shocked after the reaction that Iron Fist got that they still hired him as the Inhumans showrunner. I kept expecting to hear that they changed their minds and were bringing in someone else.
He was hired
before that reaction. He got the
Inhumans job in late 2016, and filming began in early March of this year.
Iron Fist didn't debut until mid-March.
I don't know how much he did on Six Feet Under, or Rome, but I do know he was the show runner for the last season of Dexter and that was supposed to have been a complete disaster. I haven't seen any Dexter past the second season, so this is purely second hand.
As I said, his reputation among his peers was probably already established before then. Remember, to us these are just abstract names, but to people in the business, these are people they actually know and work alongside and run in the same circles with. The viewing public with its microscopic attention span only bothers to notice what someone has done recently, but for industry professionals, this would be someone they'd known or been hearing stories about from their peers for a long time. Audiences are quick to damn a creator for a single disappointing work, because they have the luxury of distance and anonymity, but it's different when that creator is a colleague or friend, someone you've worked with in the past and have to keep working with. Besides, insiders know that the occasional failure is just part of the job, that a single project is not a whole career. So if someone's done good work in the past, they won't write them off the first time they fall short, or maybe even the second. More likely they'll just see it as a dry spell or bad luck and let them try again. Hell, if professionals were as quick to write people off as fans are, they'd quickly run out of people to hire. If someone has a consistent run of bad results, that will generally hurt their career, so it may be harder for Buck to get another Marvel gig after two disappointments in a row. But it wouldn't have happened after only one bad result, not unless it had been really egregiously awful or had failed due to gross mismanagement or something.
And as I said, it wouldn't just be about the end result that the public sees, but the behind-the-scenes mechanics of making the product, working with other producers, delivering on schedule. A producer or director can get a good reputation (or a bad one) based on factors that are invisible to us. And, yes, sometimes those invisible factors aren't about the work at all but simply about who you know, what friendships you have, how good you are at playing studio politics or being a good salesperson, etc. I don't intend to suggest that any of that is specifically true in this case, but it's important to understand that the way we see the business from the outside is very different from the way insiders see it.