He was an awesome LB, sure. That doesn't mean that he's a great coach. You have to wonder about all of the communication problems that the 49ers have, and also why they don't play Dixon more while Gore is getting beat up.
I hope the 49ers get Jim Mora, Jr. who was with the Seahawks and Falcons and was a DC in San Francisco. I think he could help them turn the corner. I just don't think Singletary is the answer.
About Croom- he may very well be the best running backs coach in the NFL for all I know. I would have to believe that a NFL position coach job would be a lot easier to handle than a SEC head coaching job, and that may be more of his cup of tea. I think he is probably better at taking orders than giving them. I do know that being a RB coach in the NFL requires very little talking to the media, which would minimize the stupid crap that he would say, it involves no recruiting, and there is no Woody McCorvey to trip him up either.
I don't know what it's like to coach in the NFL, but I would imagine that unless it is a very young player, there isn't a whole lot of teaching there. It's probably more like- "Hey, Reggie Bush! Great run! Atta boy!" Or the occasional tip "Hey, what they're doing out there is __, so we need to do __".