Why do so many Spaniards stay in Mexico?

According to the current data, the Spanish in Mexico are less than 1%. Spain's prosperous colonies include Europe (Belgium, Netherlands, Italy, Luxembourg, Portugal, etc. ), North America, South America and North Africa, so South America and Mexico were once Spanish colonies. About 20% of mixed-race people (Spanish whites and Indians) spoke Spanish during the colonial period. Since Mexican independence, whites have basically returned to China.