What Happened to the New York Yankees in the 1960's?

From 1947 to 1964, the New York Yankees won the American League pennant 15 times, and won the World Series 10 times. Then, the team fell flat on its face, and it was not seen in the World Series again until 1976. What happened after 1964? Why did the team lose its dominance in baseball? Thanks to all who respond.
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