2008 wasn't economically "disastrous" until the very end. Up until October, it wasn't too dissimilar from 2007.
http://lawprofessors.typepad.com/securities/2008/02/januarys... : "January  was a slow month for IPOs, with only five that raised a total of $892 million. This compares with ten in January 2007 that raised a total of $2.25 billion." I quickly googled, and there's probably more to look at here, since either 5 of the 6 IPOs did it in January, or there's different counting methodology in action here. Still, it's down even in months that weren't bad. It's not just statistical gaming, even if that's in play. Asking what changed is still fair.