There was and still is no realistic way for Google to switch to WebM. Not exclusively. (Yes, they can also encode their videos in WebM but h.264 versions are always necessary.)
That format would be h.264. And nothing changes.
Switching to WebM is pointless if all other browsers still can get h.264. That way you can’t change anything.
YouTube, no. Chrome, obviously YES. Firefox and Opera did and still do it. Their failure to use Chrome to push WebM means they killed off their own format. Tells you something about their priorities.