They lent the money, they didn't "give it" to the banks. The difference is that the Fed got the money back, whereas buying $2tn of debt would result in the Fed having to create $2tn.
http://www.forbes.com/sites/traceygreenstein/2011/09/20/the-...
http://www.forbes.com/sites/traceygreenstein/2011/09/20/the-...
To make it even more obviously a gift, a good bit of it was used to buy treasuries. If I loan you $100 at 0% interest, and you loan it back to me for $5 a day, aren't I just giving you $5 a day?
It all gets paid back with interest, though. None of this is anything new.