Tim O'Brien/Time

Disney's longtime leader Bob Iger has stepped down as chief executive, effective immediately, Disney said Tuesday. Iger -- who spent his entire career at the company and will leave with Disney's titanic transition to streaming, Disney Plus, capping his legacy -- will remain chairman of the Walt Disney Company until the end of next year. Disney's head of parks, Bob Chapek, is now CEO.

Iger's time as CEO will forever be marked by the launch of streaming service Disney Plus in his last year leading Disney. The launch was a massive endeavor, involving collaboration across every arm of Hollywood's biggest giant, and it spurred Disney into its $71.3 billion takeover of Fox to stay competitive. In less than three months, Disney Plus signed up 28.6 million subscribers, an unprecedented number in such a short period of time. One media analyst called it "one of the greatest product launches of all time."

With those chess pieces now in play, Iger said that "getting everything right creatively" would now be his "No. 1 goal."

"I could not do that if I were running the company on a day-to-day basis," Iger said during a Tuesday conference call about the succession. "It just obviously takes that much time and it's so complex. And so the goal was for me to turn over the day-to-day management of the company to Bob [Chapek] with direct authority over all of our businesses and basically all elements of the company, and free me up just to basically focus on the creative side. It was really that simple."

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The Disney leadership transition has been anticipated for years, but the announcement still came as a shock. The 69-year-old Iger had delayed his planned retirement several times, and the process of picking a successor was marked by some drama, such as when one heir apparent to Iger suddenly resigned in 2016. Iger's latest retirement plan had been set for the end of 2021.

The choice of Iger's successor, however, wasn't nearly as shocking. With Chapek, Disney is turning to a veteran who's spent nearly three decades at the company. On Tuesday, the board's independent lead director, Susan Arnold, said the board unanimously elected Chapek as CEO after a years-long consideration of both internal and external candidates.

But the choice of Chapek as CEO surprised some industry watchers. Streaming is one area of the business where Chapek has little experience, and many saw the success of Disney Plus' launch as setting Kevin Mayer, the executive in charge of streaming, in line to succeed Iger.

Rich Greenfield, a media analyst at LightShed Partners, was among those betting Mayer would take the reins.

"Chapek is not the technology guy when we look at his experience, which would appear critical as the tech and media worlds continue to collide; nor is he close to the content creation that is the lifeblood of the entire Walt Disney Company," Greenfield said in a note Wednesday morning. But he added that it would be "absurd to pre-judge Chapek's potential to succeed" based on those shortcomings, saying that no candidate checked all the boxes.

During Tuesday's conference call, Chapek acknowledged that technological disruption is the biggest challenge facing Disney.

"Obviously each one of our businesses, just like every business in the world, is experiencing disruption because of new technologies, new ways that consumers are choosing to enjoy our products, and we want to stay on the front end of that wave," Chapek said during the conference call. "The challenge going forward is going to be: How do we continue to have a leg up on our competition and understand when the markets are changing, and stay ahead of that so that we're proactively transforming as opposed to in any way reacting."

During his 15-year stint as Disney's CEO, Iger secured the $7.4 billion acquisition of Pixar from Apple CEO Steve Jobs in 2006, as well as the $4 billion acquisition of Marvel in 2009 and the $4 billion purchase of Star Wars studio Lucasfilm in 2012. Iger was named Time's Businessperson of the Year for 2019.

Chapek previously served as chair of Disney Parks, Experiences and Products, and has worked at the company for 27 years. Iger said Chapek "has led with integrity and conviction, always respecting Disney's rich legacy while at the same time taking smart, innovative risks for the future."

"Bob Iger has built Disney into the most admired and successful media and entertainment company," Chapek said in the company's statement. "I will continue to embrace these same strategic pillars going forward. Everything we have achieved thus far serves as a solid foundation for further creative storytelling, bold innovation and thoughtful risk-taking."

Originally published Feb. 25.

Update, Feb. 26.: With more details and context.