Why not win the queen?

In the following game

http://www.chess.com/games/view.html?id=1218718

Why doesn't white play 6.Nd6+ exd6 7.Bxd8 Kxd8

There is no reason I can see beyond simple oversight. The great smothered Nd6+ caro kan blindness mind-fugue strikes again... i've seen it before. Usually with a Queen on the e file pinning the e pawn against the king (for mate)... the bishop pinning the pawn against the Queen is new to me. 

Hey Ozzie, I had a caro kan question I hoped you could answer.. I was wondering if you had any thoughts on 1.e4 c6 2.f4!? is there a 'mainline' to this "I'll see your caro kan and raise you a King's gambit" opening? Any thoughts on playing against that?

No reason at all, he just simply missed it. This is why you can't play openings "on auto-pilot" as so many of us tend to do after so many years. Well at least he still won the game.

@JG I think people often play that with the idea to exchange and play Nf3, e.g.

1.e4 c6 2.f4 d5 3.exd5 cxd5 4.Nf3

But games explorer disagrees with me. They give the mainline as

1.e4 c6 2.f4 d5 3.Nc3 dxe4 4.Nxe4 Nf6 5.Nf2

where black's most popular move is 5... g6 which scores an astounding 69.2%.

This is from the master database, not from the chess.com database. It was a real OTB game unrelated to chess.com.

People have been repeatedly playing 2.f4 against my Caro recently, and I never understood why. However, everyone has played a weird sort of Advance variation after 2...d5 i,e 3.e5 Bf5 4.d4 c5 5.Nf3 Nc6 with equality

I have an article from chesspublishing.com on the Caro by Davies and Martin and they give only 2.Nc3 d5 3.f4, as recommended by van Geet, dxe4 Nxe4 Nf6 Ne2 as you gave above.

Yep, that advance was played against me and the continuation was similar to the line you give.

1.e4 c6 2.f4!?

Is a minor line. So minor it is mentioned second to last in Lars GM repetoire The Caro-Kann. White doesn't get anything in any of the lines. It's just good for white players who do not want to learn theory but it also accordingly grants white with nothing more then equality after a few moves.

Alot of people play this against me online. I never had problems in these lines.

Ozzie,

you're a caro guy.  Can black ever get away with h6 in the beginning if white puts a piece on g5?  I saw a game recently, Svidler (which i bet i spelled wrong) and Sutofsky (mangled that one too) where Sutofsky put his knight on g5, and if black plays h6, i'm pretty sure carnage sets in. 

Yeah, but how many of those games were between players who couldn't spot a hanging queen. ;-)

Because the Caro-Kann defense is so bad that white's positional advantage is worth more than the queen for two minors exchange.

oinquarki haha

I've since figured out that black's best is just ...Ngf6, not being scared of the double exchange on f6. Black is basically playing the 4...Nf6 variation (either exf6 or gxf6 recapture) but removing white's queen bishop and black's other knight, which gives black the bishop pair and should favor him compared with the "regular" lines.