My understanding with regards to Illinois, they wanted it in a central location. Also, Chicago is not a good location for an agricultural school. Urbana was easily accessible to Chicago via train and road. When Urbana was founded, there was an understanding that in time a Chicago campus would open. The University of Illinois didn’t have any colleges in Chicago until the mid 1890s, when several health care colleges, pharmacy, medicine, and dentistry, merged into it. Until about 1940, they were considered to be not separate from Urbana. In 1940, they were founded into their own school.
At the end of WWII, due to the GI bill, University of Illinois opened a 2 year school in Chicago aka Navy Pier, but again it was not considered to be a separate school. It isn’t until 1965, does a 4 year University of Illinois campus opens in Chicago. In 1982, it merged with the older medical campus. The state of Illinois wanted to increase the number of physicians and nurses in the state. They encouraged the medical college to open satellite campuses. Thus everything came full circle when the University of Illinois at Chicago opened a branch campus for its medicine and nursing program in Urbana. That gave birth to the University of Illinois at Chicago at Urbana.
The slowness in the opening of a 4 year school in Chicago was mostly due to politics and the perception of prestige from having only one regular undergrad campus.