I'm guessing he was a narc, but not a very malign one, and they are very common but rarely diagnosed. He saw his fake research and plagiarism as a victimless crime, so why not do it to get ahead?
To meet the clinical diagnosis for Narcissistic Personality Disorder (NPD), a person must show at least
five out of nine specific traits listed in the
Diagnostic and Statistical Manual of Mental Disorders (DSM-5). A person does not need to have a specific set of five; any combination of five or more of the following nine traits qualifies:
- Grandiose self-importance: An exaggerated sense of self-importance, talents, or achievements. JA

- Fantasies of success: A preoccupation with dreams of unlimited power, success, brilliance, beauty, or ideal love. JA

- Belief in being special: The conviction that they are unique and can only be understood by or associate with high-status people or places. JA

- Need for admiration: An excessive requirement for constant praise and attention. JA

- Sense of entitlement: Unreasonable expectations of special, favorable treatment or automatic compliance from others. JA

- Exploitative behavior: Taking advantage of other people to achieve their own personal goals. JA

- Lack of empathy: An unwillingness or inability to recognize and identify with the feelings and needs of others.
- Envy of others: Being frequently envious of others or believing that other people are envious of them.
- Arrogant attitudes: Displaying haughty, arrogant, or condescending behaviors. JA

I would say he definitely displayed the first 6 traits which is enough for a narc diagnosis. Also, making up an autism diagnosis to gain special treatment is exploitative as is gaining jobs in academia based on other people's work. He also sicced police on journalists who were just doing a job, nothing illegal, which is displaying an arrogant attitude so he has 7 and maybe all of them.
His suicide showed how important the outward success was to him - he seemed to think he was nothing without it, which is sad. His fantasies came crashing down and he was unable to appreciate what he did have, 2 kids, family and friends, his health and the ability to start over albeit in a less flashy but more real way. He could even have used the infamy of exposure to rebrand himself and do mea culpa interviews where he comes clean and does a public Come to Jesus moment. I think he really just wanted to be famous and in the entertainment industry in some capacity. It would suit him better than academia.
The memoir would have had to be pulped though.