Photo taken from this site.
I suspect that Benedict XVI could have lost his faith in the divinity of Christ, or at least could have seriously doubted it. In that case, the retired pope would probably never admit it openly, instead, he would give rather unconvincing reasons. He is just too old, and too tired for being a religious revolutionist.
Joseph Ratzinger is an extraordinarily intelligent person (he became a professor of theology at the age of 30 (*)), so it would be no wonder that he – sooner or later – might also have searched for different answers to existential questions than that provided by the Catholic Church.
Benedict XVI and Pius X were the popes most admired by me – great yet humble men.
Pius X (1903-1914). Picture taken from this site.
(*) Biographical sources: