Ask HN: Why is Hacker News so much more successful than Slashdot?

Hacker News has so many people on it everyday, which makes me wonder why Slashdot fails in comparison. I also hear that the community at Slashdot is less than pleasant, but I'm not sure as to the validity of those claims.

Why is Hacker News so successful while Slashdot has become a relic of internet history?