“Unfortunately, my own guardian angel did not prevent my injury, certainly following superior orders,” Benedict said.
“Perhaps the Lord wanted to teach me more patience and humility, give me more time for prayer and meditation,” the pope added.
There's a reason for everything. It can't be the he's clumsy, getting old or that people slip and fall sometimes. God made him fall to teach him a lesson and/or give him more time for prayer. That's how I read it.