Darn. Since the files have crypt headers, it seems like either the filename and data were crypted with different passwords (unlikely, since you said you never used another one), or it was data corruption on upload.
One question to ask, in addition to how it happened, is why didn't rclone notice it? Rclone has a check in place to verify checksums after upload -- even for crypt, as ncw explains here. Towards the end of that post he addresses a "bad ram" scenario that this wouldn't catch -- I wonder if that's what happened here?
In my reply, I mentioned one other possible scenario that wouldn't be caught, specifically due to a flaw in Google Drive. At the time, it was merely hypothetical -- but maybe this is the first real case of it in the wild?
Unfortunately, since you no longer have the original files or the Google Drive remote, our debugging options are very limited. We probably will never know for sure what happened here. 