Mike Garafolo: Saints are set to make a decision on Derek Carr within the next few weeks; likely to have multiple suitors if released

Carr is a DA signing and the Saints needing the flexibility to potentially move on from Carr was probably a major motivation in him sitting the rest of the year as you said because they had little to play for in terms of playoff positioning and did not want to risk further injury and being stuck with the old regimes QB and having the new regime stuck with Carr.
Absolutely. While I don't think Carr is the worst QB in the league, I don't know that Moore is going to want to eat up one of his "grace period" years playing a QB that isn't going to be here long term. He's going to want to set himself up to have an opportunity to get his own guy sooner rather than later. There IS a way to move off of him should they decide to start there. They could easily choose to get younger this year instead, but that is a lot more roster spots to fill than just high upside / low risk QB.