The information added some stuff insiders have apparently said:
People close to Facebook said it started to become more apparent that Messrs. Systrom and Krieger would leave after Mr. Zuckerberg promoted Mr. Cox in May to oversee all of Facebook's apps, including WhatsApp and Instagram. Around that time, Mr. Systrom expressed frustration, but he decided to stay on through the transition, people familiar with the matter said. As part of the shuffle, Mr. Zuckerberg asked Mr. Mosseri to join Instagram as its vice president of product with an eye toward one day running the team.
While Mr. Systrom and Mr. Zuckerberg had historically gotten along, their approaches to defining the direction of products were vastly different, two people familiar with the matter said. Mr. Zuckerberg’s approach is more analytical, while the Instagram co-founders managed more on feeling and emotion, one of these people said.
The departures of the two Instagram founders are the most recent illustrations of a high-level exodus at Facebook over the last few months. The list of executive who have left or plan to include head of business partnerships Dan Rose; head of product communications Rachel Whetstone; chief marketing officer Gary Briggs; vice president of communications and public policy Elliot Schrage; general counsel Colin Stretch; WhatsApp co-founder Jan Koum; and chief security officer Alex Stamos.