Timing, his next job, possible consequences to the team he's supposed to hold high in his heart, etc.
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But the management convinced him to stay, that's why he left a few weeks later. It's not like he could have refused.
Management told him to decide later after the vacation yes. You see in a corporation, each individual has a job and responsibilities that go with it. The management are responsible for who gets to be coach and so If they felt that they want to give time to an employee of theirs to reconsider his decision, then that is their call and their responsibility not his. They told him don't quit now. Take time off and think about it and when you are back give us your final decision.
Now it is possible that the employee has made up his mind fully and saw zero chance of changing his mind but it is also possible that he thought he might feel better after the break and so he told them, okay I will let you know after the vacation. He continued to feel depleted after the vacation and so he told them just that. They then hired someone else.
You see when you have a great employee in your company who plays a key role, you want to hold on to him as much as possible and so often times, managers tell their subordinates to take time off to rethink the exit. If they thought he was just another mediocre employee they'd have let him go without any fuss but they believed that he was the best guy for the job and so they tried to hold on to him and at the same time had a plan B in case that fails. Nothing out of the ordinary occured here. Neither the employee did anything wrong in taking his time before making a final decision nor did the management in trying to hold on to him (as long as they had a plan for the scenario where he decides to leave).
If Allegri had turned out to be a bad coach, then whose fault is it that the club now has a poor coach? It is management's fault not the now-departed employee.
When would the employee be at fault? He would be at fault if he left without notice at an important time in the season. If what happened was that Conte gave them the illusion that he is staying and then suddenly decided to quit then that would be bad and unprofessional behaviour. But since what actually happened is nothing more than them giving him time to rethink and him actually taking that time, then nothing wrong has occurred.
If anything, I'd have been insulted if Conte had said he is leaving and refused to even rethink the decision. Imagine Agnelli telling him we have all this rapport together, can you at least take time to rethink your decision? and Conte says no. I think the club owes him at least a rethinking of his decision to leave.
The bitterness that people have towards his departure is because the impression that we first had is that Conte suddenly left us in pre-season without any warning. That would have been definitely a shitty move and a stab in the back to the club. We only found out that this was planned by management and Conte after the whole debacle exploded and people were already hurt. A lot of people are yet to get over that first impression they had of the events.
Not only was the first impression that Conte suddenly jumped ship, it was also coupled with the horror of knowing that Allegri (who was considered an incompetent coach by a majority of serie A fans) will replace him. We felt that by jumping ship we are forced to take an incompetent coach and the whole Juve project is in danger of regression if not collapse. The first impression had us stabbed in the back & forced to use an incompetent coach in panic.
Only later we found out that management knew about how he feels from the season before and have given him time to rethink his decision and that Allegri was planned from the start. Imagine that all this was public knowledge from the start. Imagine that after our scudetto celebrations, Agnelli came out and said that Conte is thinking about leaving the club and that since we value him so highly, we gave him time to reconsider his decision and that the final decision will be announced early in preseason and that if Conte were to decide to leave, the club will hire allegri.
Who would you have been outraged at? Conte? Hell no. You would have been outraged at management and would have been panicking the entire summer and praying that he stays. You'd have pressured management to give him more money or a bigger transfer kit.
Even the scenario that you say Conte should have followed is much worse. Imagine again that Agnelli publicly said that Conte has told us he is leaving and that we told him to rethink it over the summer and yet Conte refused to even rethink it despite the club's assurance that they have a replacement lined up if he leaves. You would have been questioning his love for Juve and saying management assured him that everything is under control if he leaves.. he could have atleast gave himself time to think about it.
So try to get over the first impression by absorbing the new facts.What you thought had happened did not actually happen. Adjust your emotions accordingly.