I think the owners certainly look at whether the head coach can get the best out of the talent they sign.
SM seemed not to know how to do that and neither did NA - the only two that have been let go by the brothers.
The model is to sign potential and have them be coached to be better to serve the club whilst they are here and potentially demand a transfer fee to better the position of the club as whole.
Out of the 3 head coaches that have been brought in under their ownership 2 have gone to clubs in a higher league for compensation. It?s a pretty decent track record that deserves respect IMO.