Mnemonic

If you were to draw a person with just strokes like you see in kanji, you'd create a stick figure, maybe something like this: 大. But this is just a person, not someone holding out their arms to show how big they are. So their arms are down, which makes them look like a torso with a pair of legs. Maybe they're walking too, which is why their legs are spread out like that. You can see the person now, can't you?