All of these examples are large independent companies that operate without Amazon network. Very few French companies use Amazon to ship products, and only small ones.
Fnac and darty now have a so called "marketplace", like amazon, which means resellers. Some friends of mine ordered a Vitamix blender, which was from a reseller. The later just ordered it on amazon, and sent to him.
I find it hilarious, and a bit sad at the same time.
rueducommerce is operated by carefour, while cdiscount is operated by geant. These are the two biggest supermarket chains in France, like wallmart and costco in the US.