Jeff Bezos is stepping down as chief executive of Amazon.com Inc. to become executive chairman, marking the largest change in leadership of the tech behemoth since he launched it in a Washington state garage over 26 years ago.Amazon said on Tuesday that he will be succeeded as CEO in the third quarter by Andy Jassy, Mr. Bezos’s closest lieutenant and the longtime head of the company’s booming cloud-computing business. Jeff Bezos, 57 years old, is handing over the day-to-day reins, as Amazon’s core businesses of online retail and business-computing services are booming during the coronavirus pandemic, which has moved work and life to the internet more than ever. The company revealed his changing position as it reported that returns in the fourth quarter surged 44% to $125.56 billion-surpassing $100 billion for the first time in three-month span-and profit more than doubled.