No problem. But I do have to ask: if the switch did make an improvement to your listening experience, does it really matter why? Experience trumps theory, and you do have the experience.
Now, to answer your question, the Ethernet connection in the first place is a physical connection via a copper wire. Electrical noise can, and will travel via copper from the router or switch to your audio system, and the buffer. Noise generated from all your other stuff connected to your router, TV, streaming devices, and a gazillion of other stuff you connect to your router. Including their noisy power supplies.
And there is the clocking stuff I am too lazy and not technical to explain it to. Plenty of materials online.
Bottom line: If it works for you, so be it. Why? Who cares. You already spent the money, and are enjoying the results. Sorry this sounds crude