As no doubt have many during C-19 Lockdown.He may have ticked all the boxes & then become unwell.
When you consider the fragility of the brain it’s an absolute miracle the majority of us pass through life relative uncompromised by the stresses we are all exposed to and irrespective of if we are unfortunate to be given of “some subtle flaw” that lurks with cunning but patience for that opportune moment to surface.
IMHO no local GP can be expected to have any greater foresight into these possibilities than you or I.
K