What went wrong in Venezuela?

From Caribbean beaches to snow-capped mountains, the country has it all. It has the largest proven oil reserves in the world. Many in a thriving professional class left the country when Hugo Chavez took power in 1999, but the early years of his rule saw a massive reduction in poverty, more children in school, and greater access to clean drinking water.

That was very much "then." Now, Venezuela is in a food, health and energy crisis.

What happened?