Keeping in mind that we're speculating on a case without any direct access to the subject, it's actually really unlikely that we're looking at a single episode

Keeping in mind that we're speculating on a case without any direct access to the subject, it's actually really unlikely that we're looking at a single episode caused by one situation (his employment with Chrysler) that's lasted for thirty years. But it's entirely possible that the situation could have made existing problems significantly worse. There are certainly aspects of his writing that might be suggestive (the graphorrhea and rambling over minor details, irrational paranoia, etc.) of certain mental illnesses. Since paranoid schizophrenia was mentioned by the parent comment, take that for example: it's not something that comes about because of a single situation later on in life. There are clear, measurable physical symptoms in that instance such as a significant and measurable difference in grey matter. That doesn't happen because of any episode you've experienced.