Impact on Buñuel's career?

I haven't seen every single Buñuel film from his Mexican period, so I'm posing this more as a question than a statement of fact.

L'Age d'Or of course deals partly with religion, but it seems that after that Buñuel focused on social themes (perhaps out of financial necessity) until the mid to late Fifties. Then he made Nazarin, Viridiana, Exterminating Angel and Simon of the Desert, all with religious symbolism (either direct or more hidden). This change seems to coincide with the impact made by Marcelino pan y vino. Perhaps Marcelino inspired Buñuel to go back to religion, or perhaps he wanted to do so all along but needed a film like Marcelino to create a larger audience for religious films.