From an article it sounds like Chin was assured a spot on Miles staff but depending upon how the hiring went he could end up as a DOBO or an Asst. I think he bumped when Harriman hired on. It's all about timing. I don't know if the following is true, but this is my perception of the events.
When the hiring began Coach Miles said he wanted 1 assistant with Big 10 ties. He got that with Ben Johnson who played for Minnesota. Hot young coach with some experience and recruiting ties.
Coach Smith then joined Nebraska when CSU hired Eustacy as Head Coach. Smith has been Miles right hand man since the beginning and is an experienced assistant. He is reported to be very good with game planning and scouting and a good recruiter so it makes sense that he became an assistant. Then it got down to the Eric Strickland interviews. I think they were liking what they were hearing. If Eric was hired Chin would of been an assistant and Eric the DOBO but then Coach Harriman popped on the radar before those interviews were done. Harriman was to good to pass up. Experienced assistant with great recruiting ties both aau and internationally. His Aussie ties could payoff big time. There's a couple of franchise aussie prepsters (underclassmen) that would be awesome. His hire made it tough for Miles to give Chin an assistant spot because while Chin has some great recruiting ties and is a good teacher. He doesn't have as much college level experience as the others. The best way to leverage his strengths was to make him a DOBO, especially with the new recruiting rules.
I think if one of the other coaches were to leave then I think Chin would get promoted up and it could be that Strickland ends up as DOBO then. Of course it all depends upon timing and how far out those events are.