Think you've got the sequence mixed up here. One, Texas was colonized by the Spanish and held by them until 1822. Two, they can't have been there before they colonized it -- that's a conundrum.
One reason groups of Americans were allowed in and given land grants was to provide a buffer between the Comanches and those original Mexicans.
Correct, except that it was a Spanish idea, and the main purpose was to settle Texas with Americans who'd acculturate to Spanish rule and defend Texas against interlopers from the U.S. who would want to run up the old 1810 Western Florida flag again and "revolt" against Spain. The empresario Stephen F. Austin and his father, Moses Austin, had their commissions directly from the Crown of Spain. Moses Austin had been a Spanish subject years before, when Spanish Luisiana included his home near St. Louis. Stephen F. Austin was also a Spanish subject when he settled in Texas.
It almost worked. Then the Mexicans overthrew the Spanish colonial government of the Viceroy of New Spain. The deal lasted until Santa Anna unilaterally denounced and stamped on the Mexican constitution of 1824, which had been liberal enough to attract the loyalty of the Texians. A tyrannical coup by an Anglo-hating creole caudillo meant all bets were off, and "the conversation sorta dried up" after that.
Interesting facts about Moses Austin. I didn't know that. Thanks for your input.