The Dallas area had several universities before UTD was founded: the University of North Texas, Southern Methodist University, and the University of Texas at Arlington (though UNT had a different name at that time). These existing universities were not STEM schools.
What made UTD different was that it was founded by the same people who founded the largest technology company in the area, and they specifically founded it in order to do something about the low number of STEM graduates in the Dallas area. The TI founders went out of their way to engineer a STEM culture in a city that didn't have one just to grow some more talent for their company.
From Wikipedia [0]:
> Qualified personnel required by TI were not readily available in the Dallas-Fort Worth area because the region's universities did not provide enough graduates with advanced training in engineering and physical sciences. TI was forced to recruit talent from other states during its expansion and the founders observed in 1959 that "To grow industrially, the region must grow academically; it must provide the intellectual atmosphere, which will allow it to compete in the new industries dependent on highly trained and creative minds".[12] To compensate for this shortage they established the Graduate Research Center of the Southwest in 1961. The institute initially was housed in the Fondren Science Library at Southern Methodist University. Land for the center was acquired by Jonsson, McDermott, and Green in Richardson in 1962 and the first facility, the Laboratory of Earth and Planetary Science (later named the Founders Building), opened on the grounds of the present-day UTD campus in 1964. The Graduate Research Center of the Southwest was renamed the Southwest Center for Advanced Studies (SCAS) in 1967 and in 1969 the founders transferred the land and assets of SCAS to the State of Texas. On June 13, 1969 Governor Preston Smith signed the bill adding the institution to the University of Texas System and creating the University of Texas at Dallas.
[0] https://en.wikipedia.org/wiki/University_of_Texas_at_Dallas