That was rather unexpected.
Activision and Bungie partnered on Destiny in 2010, and with Destiny 2, that partnership continued. However, the two are parting ways now. A few months ago, Activision said that Destiny 2 was a sales disappointment and the company was reevaluating how to proceed from there. It seems like this was the best solution the two parties could come up with.
Full story from the WindowsCentral blog...