With A&M out most schools wanted to replace them with another Texas school so that they all play at least 2 games there each year for recruiting. TCU was the best option as they just won Rose and brought most football cred. This is directly from an athletic director and I posted this before TCU joined to a lot of CB disbelief.
Lastly, I strongly disagree that Houston was a better option. I am from there and my mom went to UH. It is a commuter school that is considered a tier below TCU and SMU, which both draw students from all over Texas.