Then why is the cloak not hanging down as pulled by gravity, but looking as if something holds it up? Which is exactly Aderias was trying to make you realize~
The only acceptable reason would be that his body ends in tentacles widening out at the bottom, if you base it on that principle though, the foldings would be a little less symmetrical (even if it was just gravity pulling or wind blowing from underneath I doubt these folds would look that evenly spread).
You might wish to make some tentacles crawling out from underneath, change the robe shape as if it was pulled down by gravity, or make it with something underneath, but the ends still hanging down a bit, hiding what is actually inside.