What world are we living in that people buy a physical album because they heard a new song, liked it and decided to buy the whole album?! This worked in the past but not in this gen my dear.
Sales are mainly from fanbase. Shipment/distribution and sales happen in batches and not one shot. All stores take time to process preorder sales and then real time sales. Fanbases place orders by chunk and those chunks are processed at different timing. It is the same for all groups - go check other groups
Let's not make up stories if you are not familiar with how album sales work
Let's look at other groups that are doing well, but suddenly LSF is doing differently, although they were doing well before. And yes, if a track is viral, sales can grow after a while.