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? 

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Is any human capable of beating AlphaZero in chess or go? - Quora

AI Taught Itself to Be the Best Chess Player in the World—What's

Google's AlphaZero Destroys Stockfish In 100-Game Match

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