I wonder how much of that is because they are out vs it's just a lot more efficient to send it by the pallet to grocers instead of one bag at a time to end user

I wonder how much of that is because they are out vs it's just a lot more efficient to send it by the pallet to grocers instead of one bag at a time to end users. I've seen this in other industries too - manufacturers will sell retail direct when times are "normal" because it's easy profit and they can fulfill out of "slack in the system". But when demand skyrockets they lack the slack energy to deal with retail-direct, so they just send everything through distribution.