The double confrontation between Juventus and Real Madrid in 2018 (the season Juve didn't have Bonucci, and almost lost the title to Napoli) suggested otherwise. 3-0, 1-3. It left everyone feeling Ronaldo was the only thing keeping Madrid ahead. And still, Perez refused to give him the salary he asked for.
He has such an ego, he wanted to be the one that gave Juventus a CL win, which would have been more impressive than winning it again with the competition's specialists Real Madrid.
For Juventus it was a good finacial deal, Adidas and Jeep increased their sponsorship agreements immediatly after his arrival. The fruits of which will continue to fall beyond his departure. But the rules of Finacial fair play forced the club to limit its investments, having to account for 80 M for Ronaldo each season, and instead recruit free agents like Ramsey and Rabiot without deeper analysis of said players real added value to the team.
He wasn't the only one keeping Madrid ahead, the whole Madrid team destroyed Juventus in the first leg, then got outplayed by Juventus in the second leg and got in to semis thanks to a dodgy penalty in the last minute, the penalty(who wasn't a penalty tbh) wasn't even committed on Cristiano, it was on Lucas Vasquez, Ronaldo took it, but he had a very poor game.
Then in the semis he was invisible against Bayern Munich on both legs, and then invisible in the final against Liverpool, where Benzema and Bale were the best Madrid players by far.
He was hardly the only one keeping Madrid ahead, as Marcelo and Casemiro had massive games against PSG and Juve (first leg).
Yes, he has a massive ego, he probably thought that of himself, but reality says otherwise.
Anyway, he should have never left Real Madrid, he isn't competing for Balloon D'or anymore, and won't win big trophies with average playera such as Maguire,Wan Bissaka,Fred, McTominay,etc