Honestly, I think it would have been really bizarre if something as unrelated to the central product as the design on the box, changed something as fundamental as retention of customers.
That works under the assumption that humans are purely rational beings, which we are not. Though I don't necessarily think the design chosen was a great choice based on other comments here. Maybe something a bit more generic, yet still colourful (like the candies in games like candy crush) would have been a better choice.
Maybe, and if they were selling something for display, like figurines, or even a quasi-collectible I would be right there with you. I know people who like that kind of thing, and they would like a funky box too. This is JUST candy though, it's just people buying something they want to eat. It's a different mindset, and I think, less likely to be engaged by the aesthetics of the packaging (as in the box). They're interested in the packaging of the actual candy, and the candy itself.