It is about individual talent, not the school. Period. So if they have the talent, the NBA will draft them. If not, they don't. And they still miss at times. The NBA is filled with non drafted players. From schools everywhere.
And plenty of players from blue blood programs never make it. Because the school doesn't matter, the players talents and measurables do. Not exposure, not school, not conference. Individual ability is what matters. Same as in every other sport.
And it really is not that hard to figure out.