All this shows is the different philosophies and approaches the two teams' front offices take and have been taking. The Patriots under BB have always had a "team first" philosophy and attitude and have been built for the present and the future. Pursuant to this attitude and philosophy, the Pats make sure they have good depth at QB and all other positions so that when the starter, including Brady, goes down there is a capable backup who knows the system to step in.
The Colts on the other hand have been building only for the present with Manning and have neglected to obtain good or even adequate backups for many of their starters, particularly Manning. To not have a good and capable backup for Manning on the roster requiring the Colts to have to pick up Kerry Collins right before the season began and to start him is a horrible indictment against the Colts organization and the primary reason the Colts are win less this season. If the Colts had groomed and kept a good capable backup QB, the Colts would have 2-4 wins right now.
You are also forgetting that the Colts have been in decline the last two seasons. The Colts were 14-2 two seasons ago, dropped to 10-6 and barely made the playoffs last season and this season they would have likely only won 5-8 games with Manning.
Only if you are delusional and/or completely ignore ALL the facts surrounding and associated with both situations - a good team built for the present and future with a good capable backup QB vs. a rapidly declining team with little or no quality depth at key positions including NO good or capable backup QB.