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.

A first step to a future ...f5-f4, undermining the white pawn chain.

5.axb5? f3 Black obtains a strong attack.