Since Rabbits are prey animals, they always look for things that could hinder their escape - which is anything in their path. So part of the reason they rearrange things is to move them out of the way. I think the reason they may keep moving it from one place to another is because when they move it, they don't like it there either, so they move it again, and many times it's back where it started.
For example, Rucy will move stuff while she in her pen for one purpose or another - She wants a clear path to her hiding place, or a clear path to the litterbox, or then she wants a clear path to her water dish. Then when I think she's got it all finally figured out, she leaves her pen to go play, and then returns only to find that the stuff she moved around she actually placed inconveniently in her return path.
I had a bunny once that would rearrange a blanket for hours. He'd rearrange for 20 minutes at a time, and then flop in exhaustion for 10 minutes before starting back again. He couldn't stand the wrinkles LOL. Maybe he just wanted to make it more comfortable, or maybe those upturned wrinkles were like sticks or stones to his little bunny nature, and his instincts were to "move em out" so he could have a clear path.
Some bunnies who start doing this behavior for the instinctual reasons, end up doing it just for fun. Like Rucy, she'll move or toss something out of the way, but then I swear, she just discovers she likes to play with it (like a ball with a bell) She'll take it and throw it by standing up on her back feet only and really giving it a whirl. Then she'll do it again. So funny.