Yeah, so why is Oregon, still in it?
It isn't necessarily med research, it's NIH research that's driving it.
ISU isn't in for the simple fact that most of the member schools, which don't get much USDA funding, say specifically that USDA funding doesn't really count because it's largely non-competitive (earmark vs. through competitive solicitation). Which of course isn't really true and hasn't been for a good decade.
It's probably a lot easier to get NIH funding with a med school, but schools without med schools still find niches to swim in and get a high percentage of NIH funding.
Here's what ISU is damn good at. It's damn good at getting funds from the likes of the USDA, DOE and industry. And as a result it's damn good at placing students in good jobs. It's also damn good at surveys among employers and destroys most schools in satisfaction among companies hiring its students.