You make "downloading" sound more sinister than it is. Downloading something from the network is the only way to see that it's there or know what it is. There is no substantial difference between downloading and viewing in this case.
> "With the newly obtained AWS key... I queued up several buckets to download, and went to bed for the night."
This isn't about whether viewing files on an internet is technically downloading them; this is about retrieving files of enough size and quantity that you have to queue them up for an overnight download.
Under the assumption the keys would be revoked it's just trash anyways - it'd have been useless anyways, but apparently they didnt realize how serious stuff was, otherwise they would have revoked it
A month is plenty of time to change critical S3 credentials