It did in fact happen with regularity that incapable, insane or otherwise unsuitable rulers would end up ruling.
A famous example is Charles II of Habsburg (ruled the Kingdom of Spain from 1665-1700). Suffering from several though not precisely documented disabilities due to extensive inbreeding, he died in his late thirties.
To be fair, back then countries weren’t led by nursing home escapees
It did in fact happen with regularity that incapable, insane or otherwise unsuitable rulers would end up ruling.
A famous example is Charles II of Habsburg (ruled the Kingdom of Spain from 1665-1700). Suffering from several though not precisely documented disabilities due to extensive inbreeding, he died in his late thirties.