It's called "resets". A major one happens once a year with two mini ones happening twice a year.
They will shuffle out things and flavors that did not go over so well or are no longer trendy and bring in the next hot thing.
Walmart is bad about rearranging their shelves. About the time you know where everything is, poof! it’s changed so you have to spent more time looking around for things. Sure, they think if they can get the customer to stay longer in the store that they’ll spend more money but I don’t play that game. I get ticked off and leave. In fact, they’ve pretty much lost me as a customer because of that. That’s another store that seems to have less variety than it used to.