I fall into groups 1 and 2. I am more excited about Riley than literally any other coach you mentioned as being a better option. Gruden, Harbaugh, etc. all pipe dreams, it was never going to happen. The main problem with the group 3 fans is twofold; 1- Most didn't/don't realize that it was past time for Bo to go. 2- They were delusional about possible replacements. They either wanted coaches that were never realistic or they wanted coaches that, quite honestly, would've been like the Callahan hire. Or, they wanted guys with Nebraska ties that simply are not ready yet or are not good enough.
Is the divide wider or deeper between Husker fans? IDK, it just appears to me that the group 3 folks are being a bit unreasonable. When you start with fairly unrealistic expectations and then are unwilling to give it enough time, we'll it just gets kind of crazy. People need to relax, give it some time, and see what happens. There will be plenty of time to circle the wagons. For now, it would be really nice if the zany group 3 folks could join the supportive fans group and leave goofsville behind.