I don't know what John Mackey did or didn't try. But if he wants to be a boss, well, yes, he obviously isn't much compatible with a cooperative model.
Maybe he'd have a much harder time to find willing employees (is he a choleric ass?
) if the cooperative model was better known (especially in the US) and more widely implemented.
Mondragon pretty much respects the Dunbar number, they never grow their units (departments) above a certain size.
Also in the Basque region there are actually lots of such cooperatives, so plenty of places and possibilities for workers to go, to accommodate for structural and technological changes.
Jobs and humans come first in this culture, just laying people off is inefficient for a society if you think about it. Lots of talent and productivity wasted. So essentially they give them help and support to find something new in that case, they have a sophisticated points system which records their talents and experience, which is compatible between these cooperatives. This is much easier to do than in a highly competitive environment, although these cooperatives also compete to a degree (they buy stuff not necessarily from each other but from wherever the price is right, i.e. also from the world market).