If they didn't get rid of the copyright aggreement there would have just been a fork or those people would have gone to work on other projects.
Do you have a source for this? The story appears to be the opposite - RMS was on the steering committee list since 2012 and was removed earlier this year by the rest of the steering committee as a reaction to RMS being put back as a FSF board member. https://gcc.gnu.org/pipermail/gcc/2021-March/235091.html
You cannot discuss things like this beforehand? You cannot do an RFD in the mailing list to gather feedback and questions? Even the announcement is sloppily written, because it sounds like gcc will now be licensed under GPLv3 exclusively (and not GPLv3+). This was later corrected in the thread, but confusion like this could have easily been avoided.
The announcement specifically stated that GCC "will continue to be developed, distributed, and licensed under the GNU General Public License v3.0." Until there is a revised license the "or later" is moot. One does not "continue" a policy that is a change in policy.
If this is the biggest complaint about the announcement, I think that the GCC SC did an excellent job.