The simplest, and least sarcastic, argument for the DOF model at Everton follows:
1) The Everton owner (and supporters) desire a relatively high level of success at the club
Granted, only the owner/board makes decisions as such, but here we are as supporters discussing the merits of the DOF model
2) Most people are little better than average at their jobs
Little better than average will not produce the level of success desired
3) Many successful people are successful at only one job, and not multiple jobs
"Because it worked with Moyes" is not only poor evidence against the DOF model, it's poor logic to begin with
4) Finding someone who is competent at building the club's player resources is as important as finding a manager who can assemble them into a successful playing unit; it is unlikely that Everton will find one person who can be successful at both jobs at the level of success desired; having two persons employed in separate jobs makes each easier to replace
5) The DOF model is here to stay, it's been used successfully in North American sports for 30-40 years and its only you English weirdos who don't seem to like it
*ok, it got sarcastic again at the end, SOZ