Crashing the game was in fact the goal. It was discovered by using a bot that the game would eventually bug out and start trying to read tile data from the RAM, which gave a chance for the game to crash. No human player had been able to reach this game crash until now, which is why it's a big deal. It's the first time someone has technically beaten Tetris, as normally every single player will eventually top out and lose either due to mistakes or bad luck with the pieces.