Here are a couple links to explain it. From the first one:
'Faced with mounting unemployment and spiraling deflation in the early 1930s, the U.S. government found it could do little to stimulate the economy. To deter people from cashing in deposits and depleting the gold supply, the U.S. and other governments had to keep interest rates high, but that made it too expensive for people and businesses to borrow. So in 1933, President Franklin D. Roosevelt cut the dollar’s ties with gold, allowing the government to pump money into the economy and lower interest rates. “Most economists now agree 90 percent of the reason why the U.S. got out of the Great Depression was the break with gold,” said Liaquat Ahamed, author of the book Lords of Finance. The U.S. continued to allow foreign governments to exchange dollars for gold until 1971, when President Richard Nixon abruptly ended the practice to stop dollar-flush foreigners from sapping U.S. gold reserves.'
https://www.mentalfloss.com/article/12715/why-did-us-abandon-gold-standard
