[vitus]

To add to this: rough consensus is defined in BCP 25 / RFC 2418 (https://datatracker.ietf.org/doc/html/rfc2418#section-3.3):

   IETF consensus does not require that all participants agree although
   this is, of course, preferred.  In general, the dominant view of the
   working group shall prevail.  (However, it must be noted that
   "dominance" is not to be determined on the basis of volume or
   persistence, but rather a more general sense of agreement.) Consensus
   can be determined by a show of hands, humming, or any other means on
   which the WG agrees (by rough consensus, of course).  Note that 51%
   of the working group does not qualify as "rough consensus" and 99% is
   better than rough.  It is up to the Chair to determine if rough
   consensus has been reached.

The goal has never been 100%, but it is not enough to merely have a majority opinion.

[mpyne]

And to add to that, the blurb you link notes explicitly that for IETF purposes, "rough consensus" is reached when the Chair determines is has been reached.

[cryptonector]

Yes, but WG chairs are supposed to help. One way to help would have been to do a consensus call on the underlying controversy. Still, I think the chair is in the clear as far as the rules go.