The comments in Kathryn’s Report (linked above) mention observed low performance on take off in the FlightAware data. I have not verified that personally.
I fly a fixed gear C177A much of the time in the Valley of the Sun. With one person and full fuel it is not a problem so I agree that the high DA alone is unlikely to account for this.
I think he may have been a lawyer himself and also appeared to be mentally ill. I imagine he had those in his life, such as his wife, who tried to care for him and mourned his passing.