In terms of Miami-Dade, it's not just Cubans who are right-leaning, but also Chileans, Colombians, and Venezuelans (the left-leaning Hispanic groups are mostly Mexicans and Puerto Ricans). Additionally, in Hialeah (a city with a high concentration of Cubans), the share of people with higher education is also relatively low (about 20%), which is another factor contributing to its rightward lean.
Hialeah specifically may have low college attainment, but the county as a whole is 32.5%, which is not that far below the national average.