Why did the US allow immigrants to come into the country during World War 2?

The US allowed "evacuees" of Germany and occupied countries to enter the country so they could be free and gave them the option to become naturalized if they wished to become US citizens. They wanted the immigrant's expertise. Thankfully some of them joined in the effort to fight Japan and Hitler. They were also sympathetic to the plight of the Hebrew people and welcomed them with open arms. The US is known to be the big melting pot made up of immigrants from all over the world. It is due to a German scientist who left Germany that the USA made it to the moon and developed the ability to go to space and stay in space. Some helped with the development of the atom bomb too.