In the 1980s and 1990s, legendary CEO Jack Welch turned GE into the biggest and most complex conglomerate on the planet. Now the new boss, John Flannery, is trying to fix the company by doing the exact opposite. The sell-off amounts to a rejection of the conglomerate model itself. GE wants to focus its attention on what it believes it does best: making power plants, jet engines and health care products like MRI machines.