Blaming our recruiting woes on transplants does not tell the whole story. You can use that reason for the players who came to the state after Hurricane Katrina and went to Louisiana to play at LSU, but that does not explain a lot of the other people. Part of it is just the lack of success Texas has had on the football field. Many players want to play for the best, and bad Mack Brown and Charlie Strong did not produce great results. Other players in the state have been pragmatic about wanting a good education, which is why they chose schools like Stanford. I cannot blame them for that, though it is hard for me to understand how they could possibly have time to do anything lucrative like engineering, business, or computer science at a top school while being a full-time player.
tl;dr: Quality of football, quality of education, quality of coaching, and current state of the program factor in as much as whether someone was a recent transplant.