All they gave up to get those three (a good SS, OF, and 2B) were Shane Greene, John Ryan Murphy, and Adam Warren. Basically a couple of relievers and a back-up catcher. Cashman has been great the past few years. Don't forget when he traded Chapman, Miller, and Beltran, the Yankees were actually over .500. He saw right through their mediocrity and made the logical choice.
So far Shatkins has gotten one break with Smoak breaking out. Maybe they can move Estrada, Liriano, Bautista, and Smith for pieces like Hicks/Didi/Castro on other teams. They will certainly need to in order to be competitive in 2018. That seems like more and more of a long shot.