"I believe in the team and am confident they will deliver a great game and now is a good time for me to step away," Lee said.
Interestingly, while Lee is off of Halo Infinite, he's apparently still with 343 Industries, where he's held the role of partner studio head since 2016. "Chris Lee remains a Microsoft employee and while he has stepped back from Halo Infinite right now, we appreciate all he has done for the project to date," a Microsoft rep told the site.
Lee's departure is the latest of a few recent surprises in the development of Halo Infinite. Former creative director Tim Longo left the studio in August 2019 in a shakeup that also saw executive producer Mary Olson moved to the role of lead producer on the Halo Infinite campaign team. Microsoft actually cited Lee's presence as a stabilizing influence following Longo's departure, saying in statement that "the overall creative vision and production of the game remains led by Chris Lee, studio head of Halo Infinite."
Olson herself left 343 a couple months later, in October 2019, prompting the studio to reassure fans that there was nothing to worry about—"There is no creative dilemma inside the studio, and there's no writing on the walls," community manager John Junyszek said in a Reddit post. Related or not, Halo Infinite made an underwhelming showing at the Xbox Showcase in July, and was then delayed to 2021 the following month. A full release date still hasn't been set.
I've reached out to Microsoft for more information on Lee's departure and will update this article if I receive a reply.