My view: He’s no doubt stepping down due to frailty of age. They already have to wheel him about. In days when authority counted for something, the office of Pope could afford to continue until the demise of incumbent body. Pretty sure the Rap Singer sees that his church needs a person of some strength in leadership – in these days where the church needs to respond to anti-authoritarian attacks, and worse.
“this ministry, due to its essential spiritual nature, must be carried out not only with words and deeds, but no less with prayer and suffering. However, in today’s world, subject to so many rapid changes and shaken by questions of deep relevance for the life of faith, in order to govern the bark of Saint Peter and proclaim the Gospel, both strength of mind and body are necessary”