Two things:
1) Scal has Doc's trust, but not at SF. That's not his position. Why? Did you see what Grant Hill did to him yesterday?
2) In response to you're final question, I'll answer neither. While I hope that Moore is just an insurance policy in case we don't sign Smith, I highly doubt that that is the case. In all likelihood, Moore will be the only big man the Celtics will sign this year, because Danny already knows that Smith is not going to sign with Boston. Also, we did not need anything ASAP. The Celtics are not concerned with finding a guy to fill in for KG for a couple of weeks. That would be a huge waste of money, because the Celtics have proven that they can survive and win games without KG for a few weeks. The Celtics signed Moore because they need another big for the playoffs, and not because KG is hurt.