The saturated fat thing was started as a response to the big Malthusian freakout of the early 1970s. The science was settled, according to Paul Erlich, author of The Population Bomb, and many others, we were all going to starve to death. Something had to be done to convince people that eating meat was terribly unhealthy in order to save the planet. So what's in meat and not in a vegetarian diet? Saturated fat! So the science was constructed by Ancil Keyes with the end in mind and all the data points that didn't fit the narrative were dropped from his correlational studies and the guy who wrote "Pure White and Deadly" warning about the dangers of sugar consumption was blackballed. It's as simple as that.