I think Cinco de mayo was started by a beer company to celebrate liberty from France by buying beer.
Why did the Mexicans fight in the Battle of Puebla?
"Cinco de Mayo is a holiday that commemorates the victory of the Mexican army over a far larger French force in the Battle of Puebla, on May 5, 1862. The conflict began in 1861, when Benito Juarez, then the president of Mexico, stopped paying interest on the money he owed several countries, including France."