"We are the leaders in the luxury fashion online space, no question about it," said Federico Marchetti, the C.E.O. of Yoox Net-a-Porter, from a giant television screen streaming into the glossy "Technology Hub" in West London that he opened earlier this year. On message in every way, he was doing a virtual interview from Milan. "If you want me to describe my territory, then that is how I would describe it," he said.