Help this make sense to me

I'm trying to wrap my brain around this. The most common move from Master games (albeit only 2) is retreating the white knight in this position? WTF?

i suppose it depends on how old those master games are, and whom played them. also, masters sometimes troll eachother so that is a possibility

Black seems to lose material if he brings it anywhere else

Yaaaaaaa.. Did you calculate???

First off, 1... Nc6 is not a very popular choice against 1. d4.  It blocks the c-pawn, and c5 is a common theme to attack the white center eventually.  After white plays 2. Nf3, d5 is being threatened as the Knight on c6 does not have good squares.  Instead of 2... g6, black usually plays 2... d5 to prevent white from playing it, but 2... e6 could also be played.  After 3. d5, Nb4 would allow a3 with tempo and after Na6, I suspect even 4. b4 is good to take away the c5 square for the Knight.  After 3... Nb8, now black's idea is to play either c6 or e6 to try to get rid of the d5 pawn, but white can just play c4 or e4, and white has slight space advantage.  My suggestion is play mainline with 2... d5.  Go for simple theory.

It's white's turn. The black knight retreating makes some sense. The white knight retreating makes none.

This is a daily game I'm playing and I was exploring what would happen if I pushed the white pawn to d5. Black retreats. Got it. But then white's next move is stupid, according to the Master's but I think codeman303's comment is probably germane.

Oh, sorry, you are talking about the white move 4. Ng1.  I did more research, as there was only 4 games to explore even though it says 5.  None of them contained 4. Ng1.  It turns out, this is a glitch that I mentioned to Chess.com several months back.  The Opening Explorer includes transpositions in the list of moves, which is not good, as it distorts the statistics.  As a matter of fact, once you click 4. Ng1, you suddenly have 508 games.

Yeah, the math has never worked out on those statistics. Thanks for clearly this up!