re: ...why...

This may be an unpopular take on the matter, but let me play devil's advocate:

Based on the 8 regular season rankings you provided, Manning's average ranking in all categories is 5.37 and Brees is ranked 5.12.

You can't include the post-season because the MVP award is given out before then. (Also, this wouldn't benefit Brees, as Manning had a better post-season from a statistical standpoint.)

Since 5.37 and 5.12 are virtually indistinguishable from each other, perhaps Brees was hurt by two factors:

1) The Colts had a better record. When voters were casting their ballots, the Saints were on a three game slide and finished a game behind the Colts.

2) Many uneducated voters feel that Sean Peyton is so good that his system provides a large portion of Brees's statistical outpouring. On the flip side, Manning was dealing with a rookie head coach and, for all intents and purposes, was the quarterback AND offensive coordinator.

Brees certainly deserves his due and if he repeats his numbers, he'll get it this season. But when two QBs are this close statistically, the more accomplished passer is going to get the nod. Now that Brees has his ring, I see him winning the close ones in the future. Not saying I agree with the system, but it is what it is.