talked with a friend of mine who is Juventus fan, he said relationship between Allegri and CR not the best, also it was not the best when he left not long ago and he wants to build a new Juventus which is not easy when he has CR demanding to be first eleven and he needs to be used a special way other playing to accommodate his style, its more like team has to adapt to CR than CR to the team.
also after years of titles last year they lost the title and now Allegri needs to win it back and maybe put together a good CL run and simply Allegri would fancy Juventus more without CR than with him but they are aware its very hard t move him on given his salary. also he has 1 year left at Juve, with no plans for Juve to renew with him.
(they even strugged for months to put together a deal for Locatelli and only do loan plus option for 35m euros, as they cannot afford to spend it upfront, so some fee for CR and his big salary off the wage list would go a long way for them)
Allegri wants to build a team more for the next few years,not only for this last season with CR which can limit his tactical options as everything has to go through him and if he will be benched more often than CR's ego will be a problem.
Also CR was not impressed at all with Pirlo who is a second rate manager compared to Allegri and the way Juventus failed in Serie A and also in CL. (Porto sent them home in round of 16 with more away goals, and previous year Lyon sent them out of CL in round of 16, same Lyon that fucked us as well there)