Pope Benedict's decision to stand down certainly caused much greater surprise than any action he took during his papacy.
There were no warning hints that growing infirmity was making him consider his role as leader of the world's Catholics and his announcement sent shockwaves through the Church and the faithful. Certainly, if he is feeling under strain in his role then he has made the right choice. It is no exaggeration to say that the Catholic Church is in crisis and that it needs strong and vigorous leadership from the Vatican.
There are many issues facing the Church. The primary one is to bring some sort of closure to the scandal of clerical abuse of children. This was a problem which Pope Benedict inherited but which he seemed ill-suited to deal with. He was not a charismatic figure and by temperament did not give the impression of great empathy with the victims of abuse. He may have felt great personal sorrow but had difficulty conveying that to the wider world. Indeed, he appeared to focus more on reining in those who he considered turbulent priests for their more liberal views on celibacy and the ordination of women.
Some observers feel that the composition of the College of Cardinals, many of them appointed by Pope Benedict, means that his successor will also be conservative in theological terms. Of course it would be unrealistic to expect the Catholic Church to make an knee-jerk change of direction, but it does need a leader who can relate to a laity no longer prepared to take the Vatican's instructions as gospel. It would also make sense to appoint a relatively young man who can make a firm imprint on the papacy.
There are many people who believe that restoring the credibility of the Church is a very difficult task, certainly one that will take many years.
The next Pope will need to be a good communicator and to be seen as someone who can embrace change to make the Christian message relevant again in an increasingly secular world.