LOS ANGELES—Standing on the top rim of the venerable Coliseum on a 76-degree autumn Monday, Lincoln Riley took a glance behind him at the Los Angeles panorama stretching from the Pacific Ocean to the Hollywood sign to the gleaming downtown skyscrapers. “Wow. Is this real?” Riley asked. “Unbelievable.” Southern California appeared to be asking itself the same rhetorical questions after a surprising 36-hour courtship ended with Riley in charge of restoring the Trojans to a place atop the college football world. Riley arrived in sunny Los Angeles one day after he agreed to leave Oklahoma following five successful seasons in charge. He addressed his new players on campus before receiving his official welcome at the Coliseum in what he called “a surreal moment.” “It was tough to leave the place I was,” Riley said. “At the same time, I knew this was the right thing.” The respected 38-year-old coach who …