I think this is might turn out to be a surprisingly good move on the Cardinals' part for the following reasons:
1. It comes at a time when the team really needs a boost.
Sure, don't fire Amos and give EVERYBODY, fans included, a boost.
2. It gives the offensive line much more incentive to open up holes in the running game.
So you are saying they just had no reason to do their jobs and open holes before this move ?
3. All of the players on the team will want to impress AP.
I guess they had no desire to impress CJ2K... yeah, that'll do it, need to impress the new guy.
4. Most importantly, this could rejuvenate the play action aspect of the offense which has become CP's bread and butter.
I guess he got NO so rejuvenated they only needed him as 3rd string, and then, what the heck, we are fully rejuvenated, let's just trade him away.
Get a FB to go with him. That would be huge.