The Character of Kaiser Wilhelm II
The manifold blunders that led to World War I have filled many a book, but in Margaret McMillan's version, the Kaiser gets first place. He was apparently intelligent, even intellectual, but he was also a nitwit, utterly lacking in the character of a a good leader. He was lazy and impetuous, and lacked perspective, judgement, and self-restraint.
Combine grandiosity with lack of common sense and many evils promptly follow.