I think there are two factors at play here:
- Steemit is still very small. Only ~50k accounts. So there is a strong sense of community. Compare that to, say, Twitter, which has over 300m accounts and little sense of community anymore.
- Steemit incentivses good behaviour, and being polite and friendly to each other. I suppose trolls will come here eventually. But it's only the polite and friendly posts and comments which will get upvoted.
I see what you're saying with #2, but, for example Strauss IS a troll. Just watch his TV appearances!
Heck, I am a troll. You can be a troll with the lulz of Pepe the Frog and the heart of a saint. I beg to differ on the notion that the jester and teaser must always be downvoted to oblivion by the "good people".