What's changed over the last 30+ years is the amount of financial support states are providing to their public universities. A few decades ago, state appropriation covered 70% of Iowa State's operating budget. Today, it's less than 30%.
Iowa's Republican legislators and governors have viewed the Regent universities as havens for liberal think and they've decided to punish the universities the best way they know how - financially. Meanwhile, the Republican legislators and governor divert $50 million annually from the taxes we pay to prop up the 40+ PRIVATE colleges in Iowa in the form of the Iowa Tuition Grant which is only available to students who attend Iowa PRIVATE colleges. Think of it as their higher ed version of "school choice".
Anyway, as a result of all this, the Regent universities have now become tuition driven instead of state supported, just like the private universities, and they've been forced to dramatically increase their tuition to try to stay competitive. It's a big reason why Iowa State gave up its prestigious AAU status. In short, Republicans are driving the Regent universities into the ground (just as they're doing with K-12 schools) and they've shifted the vast majority of the burden for paying for a Regents college degree to Iowa families.
Think about this the next time you vote.