Why did some people want the US to intervene in Vietnam?

Some people wanted the U.S. to intervene in Vietnam to contain the spread of communism, as part of the broader Cold War strategy known as the Domino Theory, which suggested that if one country fell to communism, neighboring countries would follow. Additionally, there was a belief that supporting the South Vietnamese government would help promote democracy and stability in the region. Advocates argued that intervention was necessary to prevent a humanitarian crisis and protect U.S. interests in Southeast Asia.