Very few world leaders are actually crazy, though some perhaps want to be perceived that way. Richard Nixon supposedly said a US president ought to seem to 'have a few screws loose', so adversaries don't mess with him too much.
But non-crazy leaders can misunderstand each other, and even more easily, misjudge public sentiment in other countries. The best example I know is Hitler's "Why now?" moment -- and I suggest this without trying to compare North Korea's leaders to Nazis in any way other than being prone to misunderstand other countries.
If you want to skip a stroll through some depressing 1930's history, scroll down to
The "Why now?" Moment