While it doesn’t make sense how a mistake like this could happen, I also don’t think this could be intentional either. I don’t see why anyone would throw their reputation into the gutter like that.
Imagine trying to explain this to a future employer.
There’s really nothing stopping one developer from pushing a commit purporting to be from another developer. You can put any name or email address you like in each commit. However, that’s something that should be caught during review, so it’s not much of an excuse.
Imagine trying to explain this to a future employer.