They were pretty lucky in the CL, though much less so than they were the year prior in 15/16
. The Bayern games were a sham. 2 incorrect red cards had Bayern spend 70 out of 210 minutes a man down in a crucial tie. The momentum shift both times it happened was very clear. The offside goals were the killing blow. Neuer playing through a broken foot (and missing the rest of the season after that match IIRC) was just icing on the cake for them.
They were also lucky in the final considering Juve very clearly looked the superior side in the 1st half despite conceding early. They were relentlessly pressing RM and attacked them hard, and ultimately scored that beauty of an equalizer. It's hard to think of any other critical matches like this where a team's 1st half vs 2nd half performance is so shockingly dissimilar. It lends credence to the stories about whatever happened during HT where all the key Juve vets were at each other's throats and went on to subsequently implode in the 2nd half. Bonucci denies fighting Barzagli and Mandzukic denies the quotes about Alves and Bonucci's alleged hatred and arguing leading up to the match and during it, but the fallout after that match suggests there's truth to it. What other reason explains swiftly selling Bonucci to AC Milan? Alves' rants about Juve after leaving them also points to clear animosity. In any case, all of this was very convenient for RM who were easily able to take advantage of Juve's chaos and disorganization, totally dominating them in the second half.
Unlike 15/16 tho, they definitely were the most superior team in the CL last season. Even if they probably shouldn't have won as things went vs. Bayern and could've ended up losing to Juve had they maintained their discipline, RM were better than both teams considering all things in the CL and domestically. Out of a hypothetical 100 games I'd say they'd have beaten Bayern like 70 times and Juve even more than that. They're simply too strong in all aspects of their squad and have a strong champions mentality which is a huge deal in the CL. And while Zidane is no genius, he is simply too damn competent to fail with the assets he has. Even if Bayern and Juve had been at their top level, RM would probably have been favorites to win that CL anyway but they wouldn't have been as unstoppable as their string of KO round results seems to suggest.