One of the mysteries now revealed is why Microsoft killed the development of its Courier tablet, which some say could have become a serious challenger to Apple’s iPad.

According to a story by Jay Greene at CNET, "While the internal fight over Courier occurred about 18 months ago, the implications of the decision to kill the incubation project reverberate today. Rather than creating a touch computing device that might well have launched within a few months of Apple’s iPad, which debuted in April 2010, Microsoft management chose a strategy that’s forcing it to come from behind. The company cancelled Courier within a few weeks of the iPad’s launch. Now it plans to rely on Windows 8, the operating system that will likely debut at the end of next year, to run tablets."

Here’s what Greene says happened. Courier was the brain-child of J Allard, known as the godfather of Microsoft’s X-Box. "At one point during a meeting in early 2010 at [Bill] Gates’ waterfront offices in Kirkland, Wash., Gates asked Allard how users get e-mail [on a Courier.] Allard, Microsoft’s executive hipster charged with keeping tabs on computing trends, told Gates his team wasn’t trying to build another e-mail experience. He reasoned that everyone who had a Courier would also have a smartphone for quick e-mail writing and retrieval and a PC for more detailed exchanges. Courier users could get e-mail from the Web, Allard said, according to sources familiar with the meeting."

Greene adds, " ‘This is where Bill had an allergic reaction,’ said one Courier worker who talked with an attendee of the meeting. As is his style in product reviews, Gates pressed Allard, challenging the logic of the approach. It’s not hard to understand Gates’ response. Microsoft makes billions of dollars every year on its Exchange e-mail server software and its Outlook e-mail application. While heated debates are common in Microsoft’s development process, Gates’ concerns didn’t bode well for Courier. He conveyed his opinions to [Microsoft CEO Steve] Ballmer, who was gathering data from others at the company as well. Within a few weeks, Courier was cancelled because the product didn’t clearly align with the company’s Windows and Office franchises, according to sources."

Allard subsequently left Microsoft, the story says.