Ask HN: How do you identify a great software developer in an interview?

Several young (fresh out of college) engineers on my team that I interviewed last year impressed me with their intelligence by way of excellent algorithmic thinking. On my recommendation, they were hired. However, several months into the job, they continue to ask trivial (read: stupid) questions, and don't seem to want to figure things out on their own. Yet other engineers, who I was not impressed by during our interview, have absolutely exceeded my expectations. They have the spirit of a hacker; they dig deep into problems, learn everything within our code base, and are invaluable contributors. How do I identify those people during an interview? Why do my intuitions seem backwards?