Arizona did face a March 16 deadline to pay the Kolb bonus or risk letting him hit the market. That deadline affected the Cardinals' approach to Manning. Mortensen's report says Manning never ruled out the Cardinals. The implication is that Arizona wrecked its chances for Manning by paying Kolb. As I recall Arizona figured its chances for getting Manning weren't great enough to warrant letting Kolb's deal void. This seemed reasonable at the time.
The Cardinals put out a statement March 16 saying Manning "is no longer an option for us" because the team decided to pay the $7 million bonus to Kolb. Arizona was guarding against losing both Kolb and Manning, at which point the team would have been heading into the draft with John Skelton as its only viable candidate to start. The Cardinals made their pitch for Manning. They would have had a better feel than anyone for their chances at signing him. In retrospect, the fit between Manning and John Elway in Denver seems to have been decisive.
All for now. The Rams and Lions are close to kicking off. I'll be monitoring that one on TV before the late NFC West games begin.