If we talk about stats, averages, and expectations, it's important to identify correctly all the input data. Even the tiny misinterpretation can completely mislead you when you work with such a small data set as 5 seasons in football.
Allegri had 5 seasons:
- 2014/2015 - domestic double + CL final;
- 2015/2016 - domestic double + CL exit in the round of 16;
- 2016/2017 - domestic double + CL final;
- 2017/2018 - domestic double + CL exit in the round of 16;
- 2018/2019 - no domestic double (only scudetto) + CL exit in the quarter-finals.
Allegri admitted that he had wanted to leave after the third season, because he felt this team reached its glass ceiling and he couldn't do more without the full-scale overhaul. But he was convinced by the management to stay for another cycle. Then instead of another cycle he had two years to work with basically the same team he wasn't satisfied with. He gave it a try and quite predictably failed.
So, the last two years weren't normal neither by club's nor by Max's standards. Those two years were the reason why Max was let go. Thus, they cannot be considered normal.
Therefore, in terms of averages, the norm for Juventus is domestic double and CL semi-finals. Pep fits these expectations, Sarri doesn't. Does that mean that it's guaranteed that Sarri cannot achieve such a result? No, of course, he's yet to prove what he's capable of with a club of such a level. And so far the only thing he brings to the table is so called "beautiful football", which has nothing to do with club's objectives.
If Sarri comes here, there's no reason to set bar lower for him. He either does what's expected or shouldn't come here. Otherwise, Max's exit makes zero sense.