Something like:
"Hey all, RC here: with the very real threat of supply-chain attacks looming around us, one of the critical financial backers of our nonprofit org gave us a deadline around tightening access to the Github Account for rubygems/bundler. We tried and failed to arrive at a consensus with the open-source volunteers and maintainers for the best path forward and were forced to make a decision between losing the funding and taking decisive (if ham-fisted) action to keep Ruby Central financially healthy. We think RC's continued work is important enough that we stand by our decision, upsetting though it might be, but want to work out a better one ASAP. We are genuinely sorry for any fear/disruption this has caused."
Something simple that just owns the fact that they screwed up and tried to handle it as best they could. Doing this proactively as soon as they made the changes and broadcasting it would have been even better, but even posting this in reply to the controversy would have done more imo...