I've been in this situation before. I couldn't take direction from anyone who thought they knew what we did better than me, since I had been there from day one and saw the thing through. Also there's resentment that they're jumping on late and riding coat tails when you've already done the hard yards.
I don't think executive leadership is actually about motivating staff per-se and more about building little fortresses to further their career ends.
But it's not just that it's specializing, it's that there's more accountability. If you're supposed to be adding function X to module Y, that's much different than "fight the hottest fire".
Sometimes people get fired because they insist on acting the way that things that started. From their viewpoint it's even reasonable: they haven't change, the position has.
Sometimes people recognize the situation and quit.
Being employee number 40 is quite a bit different than 400 or 40,000. Or number 4. Some people are able to negotiate the changes. Some bosses or CEOs can. A lot can't.
If companies outgrow anyone it's executive leadership that for whatever reason can no longer motivate and inspire their workforce.