Each judge will give points/money based on a different factor:
The robot will judge on accuracy, which according to you, you have been accurate.
The human will judge based on how difficult the reference and scale is, this usually never ends up below 3 anyways.
The snake will judge based on speed. The game is meant to be played very quickly, and the robot is pretty forgiving when it comes to mistakes. My guess is that you were just being super slow and got scored low by the snake, causing them to not give you any money.
To see how fast you should be drawing, watch the video that is in the game's description