Rajon Rondo isn't actually being traded to the Knicks. This is just a possible deal for the Celtics and Knicks to negotiate. The Celtics would trade Rajon Rondo and Gerald Wallace to the Knicks in exchange for Amare Stoudemire, Tim Hardaway Jr., and Iman Shumpert.
The Knicks are willing to trade these three players for all-star talent. They offered these three players to the Minnesota Timberwolves for Kevin Love already. The Knicks don't have a draft pick in the 2015 NBA Draft, so there goes the option of rebuilding through the draft. Phil Jackson knows he needs to make some moves to keep Carmelo Anthony happy. The Knicks would get Rajon Rondo. Who's better to make Anthony happy. Both have selfish attitudes and love the big lights. Rondo known for high assist numbers would be able to dish the ball to Anthony known for high scoring numbers. And what a better scene for Rondo. Mr. Primetime himself would love New York. Rondo is known for only having big games when the whole world is watching on nationally televised games. In New York it can feel like the whole world is watching. Imagine the Knicks with Rondo and Anthony. Imagine Kevin Love plays out the season in Minnesota. The Knicks could then try to get Kevin Love in free agency and form the NBA's new big three.
Now from the Celtics point of view. The Celtics deal Rondo off finally. The Celtics know Rondo is probably not coming back when he hits the free agency market this upcoming offseason. The Celtics also get to deal away the terrible deal of Gerald Wallace. They also add two of the best young guards. Iman Shumpert and Tim Hardaway Jr. would be great young talent for the Celtics to add although they already have Marcus Smart, Avery Bradley, and James Young. Unloading Gerald Wallace's contract helps the Celtics out this upcoming offseason. They will have extra cap space to sign an elite player in free agency. The Celtics could also tank this season getting rid of Rondo. Then they have a high draft pick to get Jahlil Okafor or Cliff Alexander. Now they have Marcus Smart, Avery Bradley, Iman Shumpert, James Young, Tim Hardaway Jr., Kelly Olynyk, Jared Sullinger, and either Okafor or Alexander. The Celtics would then be loaded with young talent. And they could also acquire a star player in the free agency.