I disagree with the other reply. I think it was his brainchild, though more recently I've only heard horror stories/shitposts about Evan's management style.
They used to be a constant good idea machine. Not just stories, but so many innovations in messaging app ux. Still remember kids going effing mad and disrupting schools when they released video chats. Still some of the coolest most Intuitive ux ideas I’ve seen.