When Satya Nadella took over as CEO, the company was lumbering and uncool. He cleaned up a toxic culture, crafted the deal of the decade, and put Microsoft back on top.

Jaime Teevan joined Microsoft before it was cool again. In 2006, she was completing her doctorate in artificial intelligence at MIT. She had many options but was drawn to the company’s respected, somewhat ivory-tower-ish research division. Teevan remained at Microsoft while the mother ship blundered its way through the mobile era.

Then, as the calendar flipped into the 2010s, an earth-shattering tech advance emerged. A method of artificial intelligence called deep learning was proving to be a powerful enhancement to software products. Google, Facebook, and others went on a tear to hire machine-learning researchers. Not so much Microsoft. “I don’t remember it like a frenzy,” Teevan says. “I don’t remember drama.” That was a problem. Microsoft’s focus remained largely on milking its cash cows, Windows and Office.

In 2014, Microsoft surprised people by promoting the ultimate company man, Satya Nadella, to CEO. Nadella ...