Newton was not the number one choice for the team, as most would probably imagine. It just happened to be, though, that their top four picks went one through four in the draft. Based on the available talent and team needs, Newton was the best option.
Agreed completely. I think they'd prefer Mizzou QB Blaine Gabbert but he went No. 1 overall to the Panthers so he's not there. Given what's in house with Arizona right now, there's a strong case for Newton.
Mocking The Draft points out that there are no bigger holes on the Cardinals than quarterback so Newton "needs" to be the pick which I agree wholeheartedly with. Newton has some question marks but he'll have arguably the top receiver in the game right off the bat to help him get acclimated to the pro game.
For the complete explanation of this pick, check out Mocking The Draft.