Open Sicilian Variation, newbie question

Question

Im pretty new and i was analyzing the opening stages of one of my recent games. I was playing white and we started off 1. e4 c5 2. Nf3 Nc6 3. d4 e6

    [StartPly "6"]

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    1. e4 c5 2. Nf3 Nc6 3. d4 e6 4. Nc3 (4.d5 Nd4 5.Nxd4 cxd4 6.Qxd4 Qb6 7.Be3 Qxd4 8.Bxd4 exd5 9.exd5 Ne7 10.Nc3 Nf5 11.O-O-O Nxd4 12.Rxd4 Bc5 13.Re4+ Kd8)

Now my next move was Nc3 (but doesn't really matter) and the lichess computer analysis marked this as a mistake and proposed playing d5 instead (leading to the computer generated variation 4.d5 Nd4 5.Nxd4 cxd4 6.Qxd4 Qb6 7.Be3 Qxd4 8.Bxd4 exd5 9.exd5 Ne7 10.Nc3 Nf5 11.O-O-O Nxd4 12.Rxd4 Bc5 13.Re4+ Kd8) which presumably has me 1.4 pawns up. I looked up this variation on chesstempo and found that it was never played in 2200+ vs 2200+ play, but used 57 times in all games of the database. In those game it lead to white winning in 82.5% of the games.
Which variations make this move "bad" in top level play (except for the fact that 3. d4 e6 wouldnt happen in the first place aka preselection against this variation)?
What are good alternative 4.?
If the d5 variation is not that strong, why does the computer engine still recommend it. Is it just an error in the way it assesses the position, is there a lack of depth / computing time?

Answer 1

I might be misinterpreting your question but it seems that you're asking something like this:

My computer says that such-and-such a variation of the Sicilian defence is really strong for white but it never comes up in games between strong players. Has my computer made a mistake?

No, your computer hasn't made a mistake. The reason that this variation never comes up in games between strong players is that it's too good for White. Black has plenty of better options than allowing White to get into this position. Black's a whole pawn down, he has an isolated pawn and he still has a lot of work to do to get his pieces into the game; in contrast, after something like Bb5 and Rhe1, White has everything developed, has full control of the open e-file and is aiming a lot of material at the vulnerable e8 square.

Black's mistake is 3... e6, which looks like it controls d5 but doesn't because white can just play 4.d5 and either win a pawn or kick Black's knight around.

Ultimately, the point of 1... c5 is to prevent White from playing d4 because, if he does, Black will exchange his c-pawn for White's more valuable d-pawn. Typically, White says "I don't care!" and plays d4 anyway, since exchanging pawns on d4 gives White a strongly placed piece in the centre. Because Black doesn't have a c-pawn any more, he probably doesn't want to play ... e5 to push the piece from d4, because that would leave his own d-pawn backward and vulnerable.

By the way, after 3... e6, there's nothing particularly bad about 4.Nc3, per se. Indeed, after 4.Nc3 cxd4 5.Nxd4, we've reached a perfectly normal variation of the Sicilian via a different move order: the normal route to that position is 1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e6 5.Nc3. Both sides have a decent position; the only problem with 4.Nc3 is that it fails to punish Black's mistake.

Answer 2

4.d5 move is strong. Black 3. e6? wasnt good. After 1. e4 c5 2. Nf3 Nc6 3. d4 your opponent should play cd4 and after 4. Nd4 e6

This variation of course doesnt exist in top level play because 3. e6 was horrid.