Many do care about Benghazi and Fast and Furious.
Lets be rational though - when a natural disaster of epic proportions strikes our nation, effecting millions of people - that becomes the main news story for a reason.
When someone who campaigns so bitterly against the incumbent President is able to work with the same administration he disagrees with to get aid to his constituents as fast as possible - that is not a bad thing. That is seriously one of those extremely rare times that we can look at our government and say "wow, hey look - they are actually not acting like jackasses!".
It is not that Sandy made anyone "forgive" Obama for anything - it just gave his approval rating a bump because he actually acted. Those that are mad at Christie for showing some leadership and acting during a crisis, IMO, have their hearts in the wrong place.
I'm not saying anything about Christie. Sandy made people forget about Benghazi. Result: He's forgiven. Just like his little mic tap made people forget about his promise to the Russians that he'd be more flexible after the election. He's forgiven. The point is if the American electorate is so fickle that such simple distractions can change their minds so easily, they don't really care all that much about those things.