Great post-mortem @cylon, it’s very comprehensive!
I think the most important action item is the formation for a formal working group overseeing/orchestrating those operations. This is the main missing thing and major improvement, which can also set a good standard for other protocols making Compound leading the governance ops practices.
In addition, I would recommend to make explicit adding pre and post checks with governance proposal. Simulations may help but on-chain conditions can change blocks by blocks. We can leverage atomicity to avoid to perform an upgrade if a condition is not anymore true or the changes break core protocol functionalities.
In the specific case, a small borrow tx in the proposal could have spot the issue and revert the proposal passing.
Looking forward for your feedback.