Coming late into this discussion......
Clearly he wasn’t up to it in multi crew flying, but were his basic flight training records for CPL / IR ever revealed?
It is invariably the case that his ability in flying light aircraft translates directly into more complex multi crew operations.
Within the first 20 hours of ab initial training, his flight instructors would know with certainty that he lacked the aptitude.
They will be reading the accident report with a certain sense of “if only we had terminated the training, he simply wasn’t up to it”.
Citing personal / private / family issues is often the standard excuse for failure to perform.
Clearly it doesn’t help ( if true?)
Harsh as it may be, resolve these issues, and then return once a clear focused mind is achievable.
The clue will lie in the ab initio training files. I would put money on it.