TJ Maxx cuts deals with manufacturers and distributors to capture overstock, overproduction and deal with leftovers called back because of label changes, etc. Let's say a major retail chain discontinues the Jaguar line. A lot of contracts don't allow for clearance pricing in the standard retail chain so the word from corporate office tells stores to pull stock, box it up, and ship it back for credit. These can end up in the liquidator/overstock outlets, both online and brick and mortar. The rest comes from oversupply conditions in warehouses, or even a willingness by a manufacturer to steady supply chains like TJ Maxx with product. I have also seen retailers pull stock because of reformulations, packaging changes, or promotions (get an extra 30% free in this package).
Bang!, for example, has been supplied to TJMaxx in two distinctly different looking packages. That suggests their stock is a mix of oversupply and old style packaging yanked off shelves in retail/mall locations.