He did the most sensible thing which was to keep the 3-5-2 and then gradually change things. I dont think im saying anything different to what your saying. We're on the same page. My point being he came in, took a winning team, took a winning formation and for first part of the season kept things rolling before tweaking and chopping changing as necessary. Sensible coach, played it safe. But then took it to a whole new level. I aint criticising him, all im saying is he played it safe for the first couple of months which aided in his success.
This is exactly what i like about Allegri, his patient approach, he calmed the tenacity down which we had with Conte. At the end it brought a system of balance. This guy deserves much praise but theres no two ways about it, his predeccessor left him a team of experienced winners, which made his life easier.