In geriatric medicine, there is a somewhat defined, albeit difficult, process of declaring someone medically incompetent to manage their own affairs; they usually are committed to specialized (memory care) facilities. In some cases, the symptoms and rationale are clearly obvious. In others...these patients can be vulnerable to less scrupulous individuals.

For a wealthy high functioning billionaire, but one who is arguably affected by dopamine dysregulation that compromises his faculties, I'd imagine it's a trickier path to walk...