Warbler said:

Were Conan's rating really bad enough that NBC would have gotten rid of him by now if it weren't for what happened with Leno's show at 10?

I don't think his numbers were that bad, I think they would have stayed with him longer and given him the necessary time to build an audience. However, the big wrench in the whole deal was Leno's prime time slot, his numbers were far below what the affiliates needed to lead in their newscasts. The affiliates started shouting at NBC Corporate and they had to listen. The only fix they could muster was trying to put things back the way they were.