I expect the GP was referring to missing the boat in responding to the iPhone after it swept away Windows Mobile.

Microsoft was late to respond, eventually bought Danger and released the Kin phone before cancelling it within weeks, and only released Windows Phone in 2010 a solid 3 years after the iPhone release.

Windows Phone was actually pretty nice to use, but they were already too late to the scene and didn't have a chance to steal ground from iPhone or android who already had solid app ecosystems.