How did the American 1965 immigration tide happen?

In the late 1950s and early 1960s, the global economy entered the first stage of prosperity after World War II. The United States urgently needs a large number of industrial workers. In order to cope with the rapid development of the economic situation, the US Immigration Bureau has made a series of plans to recruit overseas workers. By the mid-1960s, 700,000 overseas workers had entered the United States. 10 years later, more than 80% became American citizens. In the mid-1970s, the global economy developed rapidly, and American scientific research entered a prosperous period. The resulting economic growth requires not only the recruitment of a large number of junior workers, but also enough skilled workers and some professional and technical personnel. At this time, the US Immigration Bureau has formulated a new policy to encourage all kinds of overseas talents to go to the United States, supplemented by various preferential policies. Data show that 900,000 overseas workers and 540,000 professional technicians entered the United States during this period, and more than 85% of them became American citizens in less than 10 years. In the mid-1980s, the world economy, especially the American economy, developed steadily, and the United States continued its strategy of "recruiting global talents". However, due to the relative abundance of talents in various domestic enterprises and scientific research institutions, although the US Immigration Bureau has made various plans to attract immigrants again, in fact, only a small-scale immigration tide has formed during this period, with about 1.5-0.2 million people entering the United States. Due to time constraints, less than 45% of people have become American citizens. In the mid-1990s, the American economy got rid of the recession in the early 1990s and gradually embarked on the track of rapid development. At this time, US President Bill Clinton vigorously advocated the strategy of attracting overseas talents, and the US Immigration Bureau worked closely together to formulate a series of immigration policies with wider scope and more favorable conditions. During this period, more than 3.5 million people from all over the world went to the United States for work and development, and most of them entered the United States through the H- 1B visa program.