because what they have to trade to other countries isn't quality or what the other contries need or want, therefore sinking them and they don't earn anything from it
He used to live in France for a good part of his life, but when his wife died and world war 2 was beginning, he went to the United States where he held classes and remained there. He lived in the United States until his life ended at 88 years old from heart failure while he lived in New York. Although he did visit USSR during his life in the US, he never remained in USSR.