A '73 Grand Prix continued the tradition, basically a GTO in nice suit, thumbs up from me. After that the car got bulkier and heavier with less and less engine each year until it's death in 77. They are cheap for sure but I never liked them much outside the 73's. We had a 73 and a 76 in the family so I'm not just winging out random comments.

I think its a rating influenced by the percentage market value increases year over year and number of units sold or say insured? None of these are high dollar so the percentage increase can be big when you go from $10,000 to say $12,000, etc.
It probably is people younger than most of us buying the cars they grew up with?

I have a neighbor who has 2 mint 60s broncos, he bought them new and plowed snow with them. Washed every time they got dirty and stored indoors on a wood floor, they are like new. He has 5 fords trucks and broncos, 1 suv, and a 2 door by, all are black, low mileage and mint. Trucks all have plow gear.