Who understands this move?

Why Black in both positions allows a weak pawn on e5? In first position it creates a weak pawn, in second - a weak pawn and a blocked dark bishop. In both cases Black is a 2250 player. 

Hi Scottk74. In the first position Black is lost as I just found out. Checked with engine. Too much pressure on the Queen Side which Black can`t cope with mainly due to abscence of the Knight that he killed on e5 and due to weakened c-pawn. With other words one must know what not to do in this variation, hahaha. This is exactlty what I don`t like about chess, that spesific opening-knowledge is often deadly.

In the second position White does not have a pawn on c3 but on c4 and therefor Black has a potential outpost for the Knight on d4 that is supported by the "dead" dark bishop and "weak" e5-pawn. 

The two positions are played by different players in case you are curious.

I think that in the second position Black have seen this idea in a similar pawn-stracture and uses it to get his GM opponent out of familiar terretory but instead makes the queen side attack for White easier due to abscence of the Knight that with help of threats would hold the Queen side.

I recently played a game that had the same K-side pawn structure as in the first diagram after Nxe5, dxe5.  The pawn at d5 can easily become a monster at d6 if Black isn't careful.

PeskyGnat, nice game, d6-square is freed for the Knight. 

Scottk74, trust me.

I am now studying KID, holy shit how much ideas Black must know to not lose and to win.... and this is what chess is at 2000+ level, a memory game! 

Pretty much all positional concepts like backward pawns or bad minor pieces etc are lies... maybe that's not a good way to say it.  Maybe better to say everything has an exception.

It's hugely simplistic to judge a position based on something so small.  When you think something is bad for black, you have to look how able white is to exploit it.  Sometimes things that are very bad optically don't matter at all.