I can't help but feel like it's bc they suck. I'm not being sarcastic I just really suspect that this is the case.
I feel like many of them get by bc it's a little bit of a boys club mentality and bc coaching in pro sports in general seems to be the worst it's ever been. Hockey, basketball and baseball seem to be sports where the right players buoy sub par coaches into looking like good ones. There isn't much room for innovation in how these games are played tactically. We've had the better part of a century (or more) for coaches to invent or even reinvent the wheel while adhering to a relatively static rule set the last few decades. So everyone has the same baseline "playbooks". Only really, really exceptional coaches devise ways to really accentuate the unique combination of skills that their players bring to the table.
Comes out more in football. Which is why a guy like Belichick can absolutely manhandle an entire league (on an otherwise even playing field) for what would have been considered an impossible length of time before now.
Does this apply specifically to Gonchar? I have no clue. He's a relatively newer coach too so there's always room for a newer coach to take a next step.