We only see games, but we dont have a faintest clue what happens in practice. Maybe he tested and came to conclusion players arent a good fit for 4-3-1-2. We dont have attacking midfielder for a start. Berna is inconsistent and he is maybe closest to that spot we could have fielded. But he had big drop in form and with exception of game against Atletico, all his flaws became apparent in this season; lousy end product, woeful decision making. We dont have a holding midfielder for 4-4-2 because ideally Khedira is paired with Pjanic, but former has been injured most of the season. Matuidi's main strength is his athleticism, running up and down and chasing opponents so you dont want to restrict him and take away his main advantage. He lacks discipline for that role as well because you may be sure he is gonna maraud forward at one point and get us exposed. Can, Bentacur, neither is good enough imo. I think Allegri was running multitude of different scenarios in his head, tested some, threw away some others and came to conclusion with this group of players we have reached ceiling. He is the type of manager that thinks 10 moves ahead.