Popular sovereignty i think
President pro tempore is elected by a majority of Senate members voting for the office. The president pro tem: serves as president of the Senate during the absence of the president, may administer the oath of office to senators and to officers and employees of the Senate.
So he could let other men in the community be president so It didn't become a monarchy
During his time in office, Mier y Teran was concerned over the inability of incoming American settlers to adapt to the Mexican cultures. Mier y Teran's health was failing and he felt hopeless about the problems of the colonization in Texas.