No balls left unpunished.
As it already hinted long ago, now it is confirmed that his initial resources are embezzled. But never expected him to be King's right hand. In the other hand, it's also answer why King never question his lack of communication. If they were long time friends, he must know Diaz is a man of few words, and honest to the fault. He won't say anything if he's fine and will not hesitate to say things that need to be said. If king doesn't start looking himself, he'd believe Diaz is doing fine. That said, how is the king right now? Dead?
Also, being embezzled and left alone is unexpectedly a good thing for him, as it allows him to meet with his bride-to-be.