This is what sometimes frustrates coaches and players, mistakes made at the club top level have an impact on the team achievements. The efforts of coaches and players were in vain in the end, especially now that there are widespread investigations into players involved in illegal gambling. Regarding the transition period between Allegri at Milan, I think I have to agree with you, that they made a mistake there.
This actually happens more often at Juventus compared to other teams both in Italy and other European leagues. Juventus is caught cheating for things that don't actually need to be done. The last case, they falsify financial reports, simply because they are afraid of getting FFP penalties. In fact, this could have been prevented if Juventus had not forced themselves to bring in Ronaldo, even though bringing in Ronaldo was the right decision, because they managed to win the Serie A title, which in fact without Ronaldo they could have won the Title. Instead of wanting to earn more money with bring in super star, they need to pay high salary, and making their financial not in good position. Allegri, who came with an unbalanced financial condition, made him have to work hard to find players who could play according to his strategy, also not too expensive. Previous failures were normal because they were in a transition period. By now, Allegri should be able to show his abilities again as one of the best coaches in Serie A.