I thought you were referring to the students getting national merit awards, not just finalist status. The vast majority of semi-finalists become finalists (about 15000 out of 16000) and those that don’t typically either don’t bother to write the essay or other follow-up work, choose not to take the SAT, or have really bad grades. I don’t think that even one or two Cs in a high level course would keep a kid from finalist status.
The actual receipt of a scholarship is different:
In addition, there are various awards by corporate sponsors, but these are only for a certain subset that either have a parent working for the company or live in a certain area.
Beyond that are the college merit awards, for colleges that participate and finalists that list the college as their first choice.
So only a bit more than half of the finalists get a scholarship of some sort.
I bet most of the previous years grads became finalists, but maybe they did not get money (especially if they chose to go to a school that didn’t participate).