Truth in your rhetorical question aside, it really is a funny story. Mexico had a desperate need for more workers so they held up a big sign that said "Immigrants Welcome!" and gave great perks to Americans who immigrated as long as they did so legally and assimilated. Tons of Americans came, refused to assimilate (because strong men are proud of their heritage and uphold their native culture), and by the time the Mexicans realized what was going on the American settlers were sending out feelers for the US to come integrate them. The US didn't want to cause a diplomatic mess with Mexico just yet, so Texans just created their own mini United States until the day their country men wanted them back.