That's what he thinks God is calling him to do. He was too old to preform the job to the best of his ability. He feels a younger pope will lead the Church better then he will. Good for him. What a tough decision!
What would you have done? Today was his last farewell, as shown on the National News TV. He was too old to perform his duties, and his doctor told him he could not fly anymore. He did the right thing, and now someone who can perform well will take over. I don't think anything about it was "ridiculous".
I've always viewed the Catholic church as a business... so when a business leader gets too old to run his/her business... it's time to give it up, sit back and reap the rewards of the effort you've put into it.