It’s a leadership trait that most coaches (and professional leaders in general) possess. Leaders that give bad speeches, stutters and stumbles, etc. generally don’t command the same level of respect or inspire confidence to a room full of alphas, especially when the team is already failing.
Belichik is a cheap counter-example to this that’s convenient for you to use. He’s stoic by nature though and isn’t TRYING to be ra-ra. He is a rare breed and more importantly, has the skins on the wall to command the respect he gets.
Not sure if you’ve ever played sports or been around a locker room environment, but for me, this guy just doesn’t look the part in this setting. He’s “acting.”
By the way, Andy Reid is one of the best in the business at locker room speeches and firing the guys up.