Why Charlton Warren? Brasky nailed the main reason. It seems he can recruit. Of all the schools, Nebraska desperately needs good recruiters the most. Nebraska is the least populated state in the Power 5 Conferences with zero geographical scenery to attract people.
No mountains. No oceans. No beaches. No weather. No population. The only thing Nebraska has is good academics(appeal to parents and the smarter kids), passionate and knowledgeable fanbase, a community minded team set(appeals to the kids that want to be good people), and believe it or not, religion.
Right now, Coach Warren seems to bring in "highly rated" potential talent, and Pelini can coach them up. If you coach up players with potential it should work.
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There is that possiblility, I'm still hoping Bo goes so I admit my logic is affected by that possiblity (and will continue to be until he is gone).