Why is this so rarely played I won with it

5.Nd5 is the Belgrade Gambit in the Four Knights. It was one of Tal's favorites in his pre-master days. Later he recognized it was not particularly good as both 5...Nb4 and 5...Be7 give Black a superior game.

In the game you listed Black's first mistake is not 5...Nb4 but the next move, 6...Nbd5. The simple 6...Nxe4 (as in Tal - Averbakh, Riga 1954) leaves White with little compensation for the pawn. In his "Life and Games" book Tal considered Averbakh's play (up to move 11...Ba5?) to constitute a refutation of the Belgrade Gambit.

It may be a good surprise weapon in blitz and bullet, though.

8...Nf6 is not good.  Black normally plays 8...Ne7 here, which is then followed by 9.Bg5 f6 10.Bxf6! gxf6 11.Qh5+ Ng6 12.O-O-O, White has compensation for the piece, but Black is not busted.

5..Nxe4 is also good for black, so White is taking a risk when playing the belgrade gambit. Black has ways to play lively or solid if he wants. Suppose it could be played more but as a Black player when employing the 4 knights I hardly ever face it so would have surprise value in blitz.