When Sundar Pichai joined Google Inc. in 2004, he seemed an unlikely CEO candidate: a semiconductor engineer with a business degree assigned to manage the Google Toolbar, software that lets Web surfers quickly search with Google on other browsers.

When Mr. Pichai was named Google’s next chief executive Monday, he seemed the only logical choice: a protégé of CEO Larry Page who had been groomed for the job with increasing responsibilities in recent years.

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