I wouldn't say crazy. It's pretty simple. No nuclear armed state has ever been invaded by anyone. Ever wonder why the US invaded Afghanistan and not Pakistan (where all the Taliban went and got protection)?

Contrast this with Libya and Iraq which more or less complied with US demands for disarmament and inspections. Both of those leaders are dead now.

It's a very dangerous game being played right now with North Korea. They are technically a nuclear armed state. Their capabilities are still in their infancy but growing rapidly. If anyone is ever going to war with North Korea again, their window to do so is closing fast. Kim is just trying to close that window as fast as possible. Once closed, North Korea can do almost anything they want and never have to worry about a military response again.