Why did nativists want the government to bar entry to chinese government

Chinese people were migrating to the west coast to find fortune in the Gold Rush, you can imagine why they didn't like this. It was not cool for them to take away their fortune. Later on they passed an Act called the Chinese Exclusion Act, it purpose was to ban entry to Chinese people except students, teachers, merchants, tourists, and government officials for 10 years. Due to scarce work, political pressure was put on the government to restrict Asian immigration.