It's hard to tell from your picture, but it looks like a telephone line connector (RJ11), versus RJ45, is that correct? You can do a lot with wires, they don't necessarily need to be used for intended development. This looks like the previous owner was "commed-up" as a mobile comms outpost. Connections stay, equipment/cords leave when operator departs the vehicle, just one guess from many possibilities. Maybe you can make use of it, keep us posted.
Pretty sure it's RJ45 and for sure no idea why someone would.