When Neither Player Knows the Opening

https://www.chess.com/game/145461998294

In this game, both players scored <60% accuracy and with a game play rating of 850 and 900.  How can two 1500 level players, play so poorly?  The opening was the Soller Gambit, where I only know a few moves for a quick #.  Since the player saw it, and defended, afterwards was a mess of blenders, mistakes and misses.