Crème crowd or astute leaders...
This is very abstract level of attributes. It can be “at times” quite relative, depending on one’s way of perception.
I have seen such people who were a cut above than the rest but couldn’t make it. And I have seen such people who were just average in their writing skills (an important factor to get through CSS) and they made it.

I think it depends on many things; like the way you attempt the exam, your writing skills (should be easy and fluent, thus making it more exquisite), your analysis (should be balanced, no maverick approach and at times a bit of obsequiousness required).

It is a matter of “chance” and “choice (choice of your level of hard work, how much you choose to work hard)”

Since it is all about analytical and not mere concepts or calculations, it makes CSS more related to personal approach of the person who checks your paper (this thing counts more when you attempt a controversial topic). So here comes the element of chance.

Well, rest since seats are limited, they tend to select only those candidates who they reckoned “the best”. Most of the times they are right and sometimes they slip up.