During World War II the United States government rounded up 120,000 Japanese Americans and placed them in concentration camps, without trial, for the duration of the war. This is an event for another node, so we shall suffice it to say that the action was unnecessary, generally unjust, and fueled more by racism than enything else. In any event, the war did eventually end in victory. Near the end of the war and extending afterward, propaganda praising the Japanese Americans as loyal and hard-working Americans was being released into the public. This worked to counteract the propaoganda of anti-Japanese groups such as Labor Unions, and the American Legion. The government propaganda stressed the American Ideal of Equality and put forth that Japanese Americans were hard-working Americans and that they had performed remarkably in the military during the war.
Fast forward: In the mid 1960s, Twenty years after the last American Concentration Camp is closed, William Peterson, a professor at the University of California, coined the phrase "Model Minority." The term designated Japanese Americans and specifically excluded all other minorities. The term was meant to both praise the Japanese community and suggest that others should follow their lead. Mr. Petterson held the Japanese in such high esteem because they had succeeded in America on their own without government aid. Mr Peterson, being a conservative, was not in favor of helping to support minorities in any way. As a result of this he clung mightily to the Japanese cause and used it as a demonstration that it is unnecessary to help the other worthless, lazy, non-achieving minorities. He openly and specifically used the Japanese example to attack programs designed to promote Black equality in the United States.
Later, other social scientists naturalized the term, freeing it of Peterson's connotations, and used it to describe the social position of Asian Americans in general. This was appropriate because the image of the Asian in America had changed dramatically. Japanese and Chinese were considered bad minorities to a far less significant degree. Discrimination against them had decreased significantly, they had attained middle-class status in general, and other minorities were holding the attention of major racist organizations. This is not to say that they enjoyed true equality, the idea has not been invented yet.