The only appointments he got right, in my view, were Allardyce and Ancelotti - and both of those were flawed. Big Sam was appointed to ensure safety. He did that, but he was never a sustainable appointment. He was a last resort. He probably knew he'd sack him after he did what he was hired to do, and he probably knew Sam wouldn't come for the pleasure of being sacked after 8 months, so it was what it was in the end. He paid the compo.
Carlo was a stardust appointment of an owner who lived up to the club's motto. Only the best. But having snared such a top rank coach, the shame is he didn't move heaven and Earth to keep him. Perhaps he couldn't. Perhaps the lure of Madrid was always too much. But my sense is that Carlo was actively looking for a way out at that point. After all, he seemed to initiate contact with Madrid over a departure...
The appointments of Koeman and Silva were transparently doomed from the start. I would argue that the same applies to Frank. Hopefully I'll be wrong on that, but I doubt it. The Benitez appointment was brazen and, whatever the logic of appointing a proven manager with a serious track record, he really didn't read the room. Everton is a very difficult club to run. He didn't help himself there, despite his best intentions.