The Dartmouth supplements are unlike other university’s supplements in it does not ask the Why us question. Should I follow the prompt I choose and just not talk about how I am a good fit for Dartmouth or mold the prompt and my essay into a why dartmouth essay (ie. talk about the opportunities available at dartmouth, etc.)?
surely you can mention Dartmouth and what you like about it and why it fits you, but I’d say make it personal! This is another chance to make the admissions officer like you through a personal essay that is, almost all of the time, much more interesting than an essay that names professors and programs and research opportunities! Also, the essays themselves don’t leave much space for why Dartmouth, but rather hint that they want something heartfelt and personal: origins of your name and whatnot. Dartmouth is prestigious Ivy, they know you’d want to attend if admitted, thus i’d say they’re not looking for a why Dartmouth. Be creative! best of luck!