The problem is that it is hard to fire one without the other. McPhail hired Klentak. If you fire McPhail and replace him with a new POBO, you really need to give him (or her in the case of a Kim Ng) the leeway to hire their own GM, scouting director, farm director, assistants, etc... And, also if you fire McPhail and keep Klentak, you telegraph to him and the entire world that Klentak is a two-year at most lame duck. Plus, it's the same problem we had back in 2015 when McPhail and Klentak were hired--they were not allowed to hire their own people and, instead, relied upon people who in hindsight got us into the ditch to begin with. And, if you fire Klentak but not McPhail, it's more of the same of Middleton being a meddlesome owner who's really in charge (see the firings of Mallee and Kapler last year) and McPhail basically gets shown up and humiliated--he keeps his own job but is seemingly exposed as a wimp and one who made a bad hire in Klentak. When McPhail's contract runs out and he presumably slinks back into retirement, what kind of POBO would want to work here if he is going to be denied control and possibly humiliated the way McPhail was?
Really, especially with the benefit of hindsight with the way this season has turned out, if Middleton was that set on firing Kapler and Middleton and Klentak disagreed, he should have fired all three of them, especially with Almaraz on the way out the door already. Truth of the matter is that Middleton is Steinbrenner South. Unfortunately, he's the '80's version of King George--meddlesome, reckless, petulant and constantly bullying his baseball people instead of letting them do their jobs and who ultimately drove the proud Yankees into the ditch by '90 when Faye Vincent banned him--not the older, wiser sensibly-driven version of Steinbrenner who came out of banishment in the '90's and who was generous with the purse-strings but never got in the way of Watson and later Cashman or Torre and later Girardi. See also, Ed Snider for how well things work out with a meddlesome, reckless, petulant and constantly bullying owner.