Might not be that quick, but in reality John's management and the club have been working on the extension well before the North job came up. The leaking by North of the potential offer to John (before their coaching selection panel has even met) was an admission that they know the deal with Sydney is close and is a last chance godfather offer to delay it.
It is done and As usual they look stupid again for throwing outrageous amounts of cash around to not even getting close to smoking the cigar.