You can replace SOME of the oil with applesauce. But replacing all of it (which I did find on some really shitty websites) will not work correctly.
Fat soluble flavors will be diluted by the excess water as well as not giving flour anything to bond to. Less flavor, rock hard baked good.
If you want to try using applesauce, use unsweetened applesauce and only replace (at max) 50% of the oil required for the recipe. Results may vary, I don’t see the use in lowering the fat content of a delicious baked good. I’m eating that shit full flavor, full fat, full sugar. Just eat less of it.
Outside of that tangent, the gall of this person to say “I followed the recipe exactly” when their very first sentence contradicts that completely.