Just an educated guess here, but I don't know how hard Foster was being recruited by teams other than Minnesota. He really seemed to have fallen off, and I doubt he still had standing offers from Wisconsin, Illinois, Tennessee, etc. He also didn't have a great (not bad, just not great) high school season. I think it would be hard for him to find a program as good as our's to go to, especially this late in the spring.
Ellis, on the other hand, had a great senior season, and could probably play at many B1G schools. This far into the spring, though, it might be hard to find a program that still has a scholarship for him.