The real reason Chris Christie is targeting Donald Trump for his position on radical Islam is outlined within this earlier video.   You’ll note the media dropped coverage of Muslims celebrating in New Jersey as soon as the San Bernardino terrorist attacks took place.

Chris Christie was the N.J. region U.S. Attorney General at the time discussed within this video.   This CBS broadcast is from New Jersey.  The truth of the 2001/2002 era represents an uncomfortable risk to Christie:

Now compare Chris Christie’s previous obfuscations and avoidance to: