CU received an invitation because that is who the Pac-12 wanted. Baylor made a stink because they didn't want to be left behind. Their argument for inclusion was to take all of the Big 12 south, or none of it. CU gives more value to a network, but Baylor would have ensured division continuity.

The Pac-12 decided to offer CU with the expectation that Baylor would be left behind anyway. The wheels fell off when Baylor started circling the political wagons and making noise from every angle (Baylor has traditionally punched far above its weight in the political arena. It is by virtue of the school having the first law school in the state and also being founded by the Republic of Texas.) Alone, this noise wouldn't have made a difference. However, it did provide enough time for the Aggies to get their gameplan together and start making overtures to the SEC.

Without the Aggies coming along, the deal fell apart. The Aggies are a huge school and power in the state. Splitting Texas and TAMU up was too much to ask for and everyone got cold feet.

I still think had the Pac invited Baylor to go with the rest of the Big 12 south, the move would have gone through. Things were happening so fast, the Aggies would not have had time for the SEC faction to gain traction.