Quite an unnatural place for the king, but after 3.0-0 Nd4 4.Nxd4 cxd4 , followed by ...Nc6, the absence of the fianchettoed bishop leaves him rather unprotected on g1.
Turning down the rook exchange in view of his space advantage. Besides, the white rook has more prospects on a1 than its colleague on e8, such as Ra1-a6, attacking the b6-pawn.
Speeding up his development and supporting the further idea of Nd6. Now if Black swaps on f4, his active knight disappears and White's remaining bishop on b3 becomes very strong.