Because as Buzzfeed puts it, uh, apparently the threats from Trump and his legal team have just gotten to be a little much. Buzzfeed News reports that Cohen was originally slated to testify before Congress on 7 February, but now, has removed himself from that particular equation.
Multiple outlets have also floated the notion that Cohen may not have much of a choice, considering, he's under investigation and by federal law he may be mandated to testify. The newly minted House Intelligence Committee, indeed, may very well force him to do so.
The following statement was released by Cohen 's legal counsel.
Due to ongoing threats against his family from President Trump and Mr. Giuliani, as recently as this weekend, as well as Mr. Cohen's continued cooperation with ongoing investigations...