The Walt Disney Company’s top streaming executive, Kevin Mayer, resigned in May 2020 to become the chief executive of TikTok, the app for making and sharing short videos that has exploded in popularity during the coronavirus pandemic. Mr. Mayer, 58, will also serve as chief operating officer of ByteDance, the Chinese conglomerate that owns TikTok. Mr. Mayer’s departure from Disney is not entirely a surprise. Disney’s board of directors passed over him this year when it was looking for a successor for Robert A. Iger, who abruptly stepped down in February 2020. Mr. Mayer has relished working on services like Disney Plus, which rolled out in November and now has about 55 million subscribers — a runaway hit. Disney Plus will arrive in parts of Asia and Latin America this year. Hulu, which has about 30 million subscribers, and Hotstar, the leading streaming service in India, have also been part of Mr. Mayer’s portfolio. Mr. Mayer is best known as Disney’s longtime deals maven. Before running the direct-to-consumer and international division for the past two years, he served as Disney’s chief strategy officer, helping to orchestrate the purchases of Pixar, Marvel, Lucasfilm, most of 21st Century Fox and BamTech, a technology company that specializes in streaming video. Mr. Mayer joined Disney in 1993 before leaving in 2000 to run Playboy.com. He soon returned to Disney to work on Go.com, a web portal that eventually failed, and other Disney websites, including ESPN.com, before moving to strategic planning. Mr. Mayer will remain in his current home in Los Angeles, though he will travel frequently to Bytedance’s headquarters in Beijing, as well as TikTok’s major offices in New York, London, Japan and India, a spokesman said.