He was arch-conservative but not as much as many expected. And obviously he set the groundbreaking example of retiring. After JP II's performance art of persevering to the point of near paralysis, I was sure every pope for the next century or so would be carried off the throne.
But Benedict established it's more important for the church to have a pope who can fulfill some reasonable physical requirements of the job than the pope's personal limitations are accommodated. Also, he did so with the knowledge that Bergoglio, in many ways nearly his philosophical opposite, was the favorite to succeed him.