To assume that a fantasy is based in reality is a simple fallacy. Without knowing which aspect of anime you are referring to, I cannot pinpoint exactly what you wish to be explained. One common artistic inconsistency with reality that anime has is the large eyes that characters, and it is perfectly understandable for this anomaly to occur in animation because through the larger eyes the viewer is able to read the character's emotions more easily than when it's a beady-eyed character that would be more accurate to reality. Being able to convey emotion as a storyteller is a very important and strong tool.