Tucson is also home to University of Arixona that turns out large graduating classes. Part of the growth in Arizona has been due to college graduates that stayed in Arizona after they graduated from college even if they were fromArizona or not. That has not been the case in Illinois for a very long time.
About 20 -25 years ago there was a front page article in Wall Street Journal about engineers and job offers and amenities in cities where they had job offers. It specifically cited that CAT was running into headwinds in recruiting engineers because so many also had job offers from Texas Instruments in Dallas. So it became a choice of Peoria vs. Dallas.