That's a beautiful song. The white Texans were largely a bunch of grifters, speculators, ne'er-do-wells, conmen, and their lot, mostly from the slave states in the US. Even Daniel Boone was nothing more than a self-promoting personality. They had their land they'd squatted on, their slaves, their cotton, and they didn't want the Mexicans authorities tell them how to live, so they didn't pay their taxes. They made up conspiracy theories (though they weren't called that) about how Santa Anna was a dictator and a despot coming to take their freedoms. Sounds almost modern day, hmm.
Sam Houston got lucky at the battle of San Jacinto and as soon as they got rid of the Mexicans they proceeded to kick out and erase their Mexican-descended allies, including Lorenzo de Zavala, Juan Seguín, José Antonio Navarro (who helped write thee constitution and served in the Texas Senate) https://www.tsl.texas.gov/lobbyexhibits/struggles-tejano