Moyes got rid of our successful backroom because to do so provided him with extra job security, there's no other logical reason.
And further still, it was the first sign of how cautious and self doubting Moyes is as a manager.
There's no way Moyes, coming from Everton, could've thought for one second that replacing the championship winning coaching team of Phelan and Rene with Steve Round and Phil Neville would improve Manchester United...no-one would entertain such a notion.
Rene and Phelan trained this squad, remember, and we know that SAF would delegate tactically massively to Rene. These were coaches that the players famously got on with and respected - look at RvP's quotes about Rene, and look at his quotes now...look at the squad spirit last season compared to this season for heaven's sake.
If Phelan and Rene had stayed in their previous roles it would've given Moyes the opportunity to learn, and it would've eased the transition.
I'll reiterate that Fergie didn't train these players, as it's a crucial point. It's quite possible that the departures of their every day trainers effected some of the players more than the departure of Fergie did.
So why not keep them? What possible benefit could come from replacing them with Round and Phil Neville? They weren't kept, in my opinion, because their presence - should Moyes fail to do his job properly - would almost certainly equal less time in the job for Moyes...
Since Moyes has failed to do his job properly we can quite easily answer the following hypothetical: if Rene and Phelan were here right now, and Moyes were struggling this badly, would it be more, or less likely that he'd be removed from his position and the pair of them would be given the wheel until the season's close? The answer is fairly obvious.
But without them, and indeed without any worthwhile number 2, what option do we have but to keep Moyes 'til at least the end of the season?
The irony, of course, is that if he'd kept them we wouldn't be in this mess. But as we've seen over years with Moyes - he is a guarded, cautious and most crucially to this point - unconfident manager. He doesn't have the ego or self-belief needed to see that keeping those two would actually help him, he would've viewed their presence as a threat and thus they had to go.