Edit: apologies for the grammar, too late at night to be online lol
I think it's multiple factors, unique to each situation. What I had working for me was:
a) Perfect "fit." Having a Personal Statement that almost word for word fit the learning style for the Case (unintentional) , then further reinforcing this in secondary essays, and the scholarship essay. Actually feeling that Case was in the top 2 schools I applied to/interviewed at.
b) Having been accepted by my state school, so Case knew I had a cheaper option. On the flip side, I hadn't been accepted by any top 10 schools at that point, so there was a good chance I would be interested in Case, if the price was right.
c) Giving the best interview of my life. Case was my last interview out of 9, so I'd had a lot of practice, plus lucked out by being interviewed by people with same interests as me( again, fit!).
d) Great stats, which helps even though not the best ECs.
e) Case is in Cleveland, which unfortunately has the perception of being a bad city (I've had fun here thus far). Thus might feel it needs to "woo" people a little more.
honestly, it's a crapshoot. There are too many things you can't control. Like, if I hadn't got accepted to my state school, my only two options come scholarship time would be Case and Hofstra (schools with almost exact same curriculum, negligible cost difference, but HUGE difference in reputation/research opps), and both the committee and I would've known where I was gonna go, thus no need to sweeten the pot.