This is the right answer. I went to school in Hoboken NJ, which is right across the river from NYC. It was the early 1970s and the city was a den of filth. Times Square and that area was all movie theaters showing porn and strip clubs/ peep shows. It was filthy. The entire city was filthy. The murder. The murder rate peaked at the end of the decade when over 3000 murders per year were committed. When I graduated I went to work in the city and I could not describe in words some of the awful, disgusting things I witnessed, including dead bodies laying on the sidewalks in broad daylight as people walked by like the bodies weren't even there.
But I believe things began to change in the late 1960s. Movies and entertainment were once all about good triumphing over evil. Bad guys were vanquished in the end, and everyone lived happily ever after. But in the 1960s, with the war in Vietnam raging, there emerged an idea that God is dead and evil was taking over in his absence. There is no better example of this than Roman Polanski's "Rosemary's Baby". This was one of the first movies where evil was not vanquished, and in fact, Satan came out on top. I thought it was actually an awful movie with horrible characters, some bad acting and silly dialogue, but critics loved it. Shocking.
In any case it seems to me that from then on, things took a turn to the darkest side of humanity, and Hollywood started a trend of trying to outdo the last evil character with one even more evil. Of course this was probably driven by money. Bad guys that did not die in the end could be resurrected in sequels to make even more money!