Only possible with cheap oil.
No, the car companies paid cities in the 50's to tear up light rail tracks so they could sell more buses and cars.
Yes, all parts of the puzzle, but ripping up the tracks made it more difficult for folks to get around without a car. Get a car and you need to park it someplace, so why not move out of town a bit. And then the snowball starts with strip malls . . . Urban planning in the 50s was a nightmare and is the root of a lot of problems we have today.