Wait, what? For the first time in his career, Nadal was NOT the favorite going into RG. Nobody thought he had a chance in hell against Novak. His results that clay season were a semi final straight set loss to Novak in Monte Carlo, a loss to Fognini in the QF at Barcelona, a straight set loss to Andy freaking Murray in the final of Madrid, and a QF straight set loss to Wawrinka in Rome.
Other than Nadal fanboys. people with unshakable faith in Nadal like Kieran, and paranoid Roger fans like Darthfed, nobody thought he'd win Roland Garros, especially once the draw was out. That doesn't mean nobody thought he has a chance in hell to win the tournament, but rather, that it would be unlikely, and if he were to play Novak, he's toast.
For reference, here's the thread from these very forums, along with the poll, and predictions:
https://www.tennisfrontier.com/tennisforum/threads/2015-french-open-qf-djokovic-v-nadal.4265/
This is not revisionist history.