We are most definitely NOT the only animal that eats a high fat diet.
Hyenas have some of the strongest jaws in the animal kingdom so that they can crack open bones for the marrow.
Carnivores typically "eat the guts out" before going for "lean" meat (if they even bother with the "lean" at all.)
And even herbivorous primates such as the gorilla derive the vast majority of their calories from fat, the only difference being that the fat is produced by bacteria in their digestive "barrel" rather than sourced directly from their food.
"This is also the case for herbivorous primates such as the gorilla. Even thought they eat a "plant based" diet, their gut bacteria turn it into short-chain fatty acids... The mean macronutrient can be broke down as fat=.05+.4, protein=11.8+8.2, available carbohydrate=7.7+6.3 and dietary fiber=74.0+12.9. Otherwise, 25% of energy as fat, 24.3% is protein, 15.8 % available carbohydrate, with potentially 57.3 % of metabolized energy from short-chained fatty acids derived from the colon fermentation of fiber (Popovich, etal, 1997)."