Up to last night, nobody though there was a good chance of KMart getting traded. The management and ownership have been very consistent in insisting they had no interest in trading Martin (other than can't-refuse offers). The trade chatter confirmed as much, with every indication that offers for Martin were being rebuffed. 

So, either the Kings are best team in the league at keeping secrets. Or, something happenend in the last few days that changed the Kings' mind on keeping Martin and they felt they needed to pull the trigger now.