We do live in interesting times – a pope quitting on the job, something that hasn’t happened since the Renaissance. It is time, therefore, for idle speculation, which is all one can do when it comes to the Vatican. Even the highest-ranking cardinals may not know the mind of the Pope, so we can expect quite a lot of speculation coming out of Rome as well.
For what it is worth, I expect there are several reasons Benedict XVI took this unusual step.
1) His health has been deteriorating and he is probably on a downslope that involves debilitation and death. He was as close an eye-witness as possible to the decline and death of John Paul II. That was a spectacle that attracted a great deal of ghoulish interest from the press and the faithful, however much John Paul II felt he was setting an example of stoicism in the face of personal suffering (and in his case, it helped his odds of being viewed as a saintly figure). Benedict XVI is a much more private person and does not want to be an object of either ridicule or veneration while his body gives out on him in public.
2) He was supposed to be a caretaker pope, keeping the seat of St. Peter occupied while the College of Cardinals deliberated on selecting as his successor a much younger man who could serve for 20 or more years and revitalize the church, which is in serious decline in Europe and North America. He’s now served nearly 10 years, well past his sell date, and will probably live at least five more in a semi-invalid condition. He may have even made a commitment to key members of the College of Cardinals that if elected he would resign after ten years.
3) He sees this step as a gift to the Church, setting a precedent that will now allow popes to gracefully exit the world stage, just as cardinals are required to retire at age 80.
4) He has lost control over the Curia. This is the most serious of his problems. He has tried to break the stranglehold that the Italian cardinals have had over the Curia for centuries, by bringing in non-Italians to run key Congregations (departments). This has failed. The pushback has been terrific, culminating in the disgraceful theft of his personal papers by his butler. It is as if Machiavelli has been let loose in the Vatican, with intrigue and whispering becoming the order of the day as quotidian responsibilities are neglected. He has clearly shown himself to be incapable of controlling the Curia with the iron fist necessary, and obviously people under him do not respect him as a leader. He probably feels he has disgraced the papacy, and some of the older cardinals may have urged him to resign rather than let the institution of the Vatican (which is after all a government) fall into ruin.
There will be considerable speculation coming out of the United States that the revelations in Los Angeles regarding Cardinal Mahony’s obstruction of justice in the face of pedophile criminal behavior will also implicate Benedict XVI. As Cardinal Ratzinger, he clearly knew all about this situation. Nothing can harm him now; he is a head of state. The worst that can happen is that his reputation is damaged, but the Church has already been severely hurt by these scandals and Benedict XVI’s reputation sullied to a great degree. I doubt this was high on his mind in making his decision, but one never knows.
In any event, we will soon have a new pope, and Lord only knows who that will be.