Exactly one year ago, San Francisco-based First Republic Bank was sold by regulators amid a US regional banking crisis. Citizens Financial Group, which had seen the sale as a chance to turbocharge its private banking ambitions, lost out to JPMorgan. But far from being the end of the story, that failed bid was just the beginning. Within weeks the bank had announced First Republic’s Susan deTray as the head of its new private bank, a unit that is now at the heart of a fast-growing wealth franchise.