How did Google's AlphaZero beat the world's best chess computer?

Google’s AlphaZero, after just four hours of training, last week trounced the highest rated chess engine in the world, Stockfish. How did it do this? 

AlphaZero: Four Hours to World Class from a Standing Start

Google's AI became the world's best chess player in just four

From Zero to Master in Hours: AlphaZero Accelerates Reinforcement

Google's AlphaZero AI Beats World's Best Chess Software

DeepMind's Go playing software can now beat you at two more games

AlphaZero: the new king of chess - De Econometrist

Google DeepMind's 'superhuman' AlphaZero computer taught ITSELF to

Is AlphaZero really a scientific breakthrough in AI?

Google's New AI Is a Master of Games, but How Does It Compare to