I recall that it was known that he had dementia, although may be not how serious it was, at the time that he was chosen to investigate Trump. It may be that he was chosen specifically because it was known that he had dementia.
“It may be that he was chosen specifically because it was known that he had dementia.”
Just like Biden was chosen to run for president.
He was hired to give a respectable face to this abomination.
To be a sound mind was not a requirement, or it would be rather impediment to this role.