Was this in a small city/town? The car transactions sound bad, but is it possible he may have had a personal friend at the dealership? This might have been a personal favor for someone whom he wanted to benefit financially without blatantly handing out cash. It's not unheard of for a group of local businessmen to foster relationships this way.
Far from small town, and nothing behind the scenes, just a case of trusting, and/or failing to do due diligence, that resulted in a spectacular screwing.
I have run into this before, as it relates to the inner circle of local businesses. I spent my career as a small builder in an area that transitioned from a very rural, slow, nearly Amish like, very old blood community, to one that, over the span of two decades, exploded as an extremely overgrown, overpopulated, distant suburb of NYC. I was not a local, in an area where there was a massive advantage to being born in the local hospital, into a family that was there for at least a century. I knew a lot of the local power brokers and business owners. They considered themselves to be the elite, and would work hard to do business with each other. The funny part was that many of them took great delight in screwing other good ole' boys and their families. I witnessed deals in areas as diverse as remodeling and new home construction to new car sales, where the buyer got really, and thoroughly screwed. This was all done with smug satisfaction on the part of all parties, and I half expected that they would someday admit to having a secret handshake as part of their little club. The funny part was on a few occasions I knew the victim well enough to tell then that they were an idiot who paid far more than the average "move-in, flatlander" would of. This was always met with disbelief, as in, "my daddy bought his first Chevy there before the war, there is no way that I could of gotten a better deal anywhere else" OK stupid, you convince yourself of what you need to believe, to keep the game going, but I can't see wasting my hard earned money trying to be a member of the "club". OTOH, I knew several old school locals who were on to the game and told me of having spent 40-50 years having everything, from the lumber to build their homes, to every appliance and new car, shipped in from forty miles away, since THEIR daddy taught them how to not get screwed by the local good ole' boy network.
The network is long gone, there are Lowes, Home Depots and huge car dealerships all over the area, and the majority of the population came from somewhere else. Humans sure are interesting to watch, and it was a fascinating time to be a part of the local community. I'm sure the FIL was involved in the same game and probably bought more then a few cars from the same place, back when he and the salesman were the same age, and played high school ball together. The problem is that he still trusted the place, even though the kid selling him the car was fifty years younger and had no soul.