Final answer:
The Texas territory was combined with Coahuila instead of being given control of its own territory due to Mexico's desire to encourage settlement, the accessibility of land through installment payments, and the belief that it was a patriotic duty to expand American culture and slavery.
Step-by-step explanation:
The Texas territory was combined with Coahuila instead of being given control of its own territory like the other Mexican states due to several reasons.
Firstly, Mexico wanted to encourage settlement in the region of Coahuila y Texas. Like Spain, Mexico passed colonization laws to encourage immigration, and thousands of Americans, primarily from slave states, flocked to Texas. The soil and climate offered good opportunities to expand slavery and the cotton kingdom, which attracted more settlers.
Secondly, Mexico allowed buyers to pay for their land in installments and did not require a minimum purchase, unlike the U.S. government. This made land more accessible and appealing to American settlers.
Lastly, Mexico was seeking to populate the lands beyond the Mississippi River and believed it was their patriotic duty to bring American slavery, culture, laws, and political traditions to those lands, including Texas.