I believe it was because the government was afraid that they might be spies for Japan, so they thought it was safer to keep them in one place so it would be easier to keep an eye on them. It also stemmed from racism due to the attack on Pearl Harbor and the U.S. fighting against the Japanese in the Pacific.
It essentially said that the Jews were not human and were to be treated as such. The goal of the Nuremburg Laws was to distinguish what Nazi Germany perceived as ethnically pure and impure populations. It assigned people with Jewish heritage as property of the state, giving them no rights. Jews were also strictly prohibited from reproducing. The Nuremburg laws also gave strict ethnic standards to the rest of the German people, which classified them based on their ancestors race.
