It started in the W3C and the IETF group was added later. But thank you for pointing out that a lot of effort is put into making these standards a joint effort

It started in the W3C and the IETF group was added later. But thank you for pointing out that a lot of effort is put into making these standards a joint effort across the industry. (I was one of the original authors in the W3C but left shortly after the BoF happened).