In a time when Calories are at a premium, fat indeed is good. A working man ca. 1900 struggled to maintain weight, usually, so fat was used in a diet of cheaper foods in things like gravy, fried foods, eggs, etc. Wealthy folk were fat, working folks were slim.
Fat is a cheap way to infuse flavor, which humans prefer because WAY back every Calorie was a struggle, hunter gatherer days. The first fat man must have been a novelty, some king or high official in some developing civilization. Likely it was viewed as a mark of status.