By handing over the open file White manages to push his kingside pawns.

Provoking Black's next move so that a later f4-f5 is effected with tempo.

This lets White continue his plan, eventually leading to a strong attack. Correct was:
6...Qd4! 7.Qxd4 Nxd4 8.Rd1 Ne6 with just a slightly inferior endgame.

Or 7...d4+ 8.Kg1 , followed by Qg5, with similar play.

Deflecting the rook from the defence of the d5-pawn. The game concluded:

Black resigned.

Covering the rook on d8 before moving the knight from d7, where it controls the crucial square c5.

After 3.Rxd8 Rxd8 4.Rxd8 Kxd8! White doesn't achieve c4-c5 either, just like in the main line.

Preparing ...Qe7 with some pressure on the b4-pawn. Black has no problems.