Bob Geldof grew up listening to the radio on the outskirts of Dublin, where his loneliness and resentment of prescribed drudgery manifested itself in an all-consuming desire to escape. It was an almost quintessential rock-star story — rebellion, transgression, fame, drugs, escapades, fading glory. That is, until he turned on the news one late-October evening in 1984 and saw a short story about a famine that moved him and changed his life. The next year, Mr. Geldof was in the Sahel region of Africa, overseeing distribution of the $140 million he and his fellow musicians ultimately helped to raise in one of the largest charity efforts ever organized.