Because it's not "impossible." Liverpool also managed to sign Lambert, another player who is at the World Cup. Like any other time, you have to actually make a bid and then it becomes possible. However when the season starts and we've still not signed anyone no doubt we'll told by Wenger that we couldn't do anything because of the World Cup.
Anyway hopefully this will now put to bed any worship Arsenal fans still have for Fabregas. Won't be long until he comes out with something about having "London DNA." So much for that Barcelona DNA. Didn't last long did it? Twice.
Also is it possible that Wenger turned it down because he doesn't want to spend on that much on anyone rather than because he didn't want the player which we all assmume?