For decades, Warren Buffett had a simple rule that shaped his entire investment philosophy: “Buy what you know.” And if there was one thing Buffett made crystal clear, it’s that he didn’t know tech. He joked that smartphones were “too smart” for him. He didn’t keep a computer on his desk. He tweeted only nine times in four years, because — in his words — the alternative was “going to a monastery.” So when people asked why the Oracle of Omaha wasn’t buying flashy tech stocks during some of the biggest ...