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.
1...Nxf4 2.Qxf4 Kh8 would be better. But after 2...Bxe4 3.Rxe4 White is much better thanks to his strong bishop and the weakness on f7.
This lets the d-pawn advance, but after 3...Rad8 4.Rad1 that pawn should also tell in the long run.
4.Rxe8+ Rxe8 5.Bxd5! cxd5 6.d7! Re7 7.Rc1 Rxd7 8.Rc8+ Rd8 9.b4! Qb6 10.Bc7