Replacing 1-CD radio with 6-CD radio

My 2007 Prius came with a 1-CD radio and a 6-CD changer below it. The changer died and the radio got a knob snapped off, so I purchased a used 6-CD radio to replace both.

Never in my wildest nightmares did I imagine that the radio wiring harness would be specific to the radio the car came with! The Gen 2 Prius had at least 3 radio options; possibly more. Why and where on Earth did an electrical engineer decide to go with a wiring harness that only connected to one radio?! Or did the 6-CD radio have an adapter / dongle between the 'base' harness and the connectors on the radio?

I cannot even cut the 1-CD radio connectors off the harness and splice in the 6-CD radio's connectors because the used radio did not come with any external wiring (its connectors).

Any suggestions, information, or assistance would be greatly appreciated. I allotted 10 minutes to swap out these radios. I'm already 10x over that expected time investment and have gotten nowhere.