I'm not sure how automated deployments would have solved this problem. In fact, if anything, it would have magnified the impact and fallout of the problem.
Substitute "a developer forgot to upload the code to one of the servers" for "the deployment agent errored while downloading the new binary/code onto the server and a bug in the agent prevented the error from being surfaced." Now you have the same failure mode, and the impact happens even faster.
The blame here lies squarely with the developers--the code was written in a non-backwards-compatible way.
Substitute "a developer forgot to upload the code to one of the servers" for "the deployment agent errored while downloading the new binary/code onto the server and a bug in the agent prevented the error from being surfaced." Now you have the same failure mode, and the impact happens even faster.
The blame here lies squarely with the developers--the code was written in a non-backwards-compatible way.