Why did southern Republicans lose power during the 1870s?​

The correct answer is D. They supported the abolition of the constitution by Santa Anna.

Explanation

During the early 1800s, many Anglo-Saxons were exiled south to the region where Texas is located. This developed a conflict between the natives and the settlers who came to settle there. During the establishment of the Federal Constitution of the United States of Mexico of 1824, the Anglo-Saxons who have settled in the Texas region agreed with the abolition of said constitution, supporting the vision of the Mexican conservative forces led by Antonio Lopez de Santa Anna. So the correct answer is D. They supported the abolition of the constitution by Santa Anna.