They weren’t so much poor people, as people willing to settle in the frontier, bringing goods and civilization with them. Look up the Old Three Hundred. Mexico won independence from Spain and established a new constitutional government. One implication I learned o so long ago was that they were seeking to disperse the Indian population in Texas, as you had the Apache and Comanche and Karankawa, as well as the Kikapoo and Alabama-Coushatta Indians. The Karankawa were among the most feared.
I will look up the “Old Three Hundred”! Thanks.