No one wants to deliberately act against his interests. But due to foolishness (and therefore mistakes) it happens. Do the leaders of Steemit completely free from making mistakes?
This is true but it has nothing to do with Steem. No system can protect you from human mistakes when intentions are good. All we can do is align the interests of those who have power with the interests of the whole system. And this is what Steem does. There is no other way.
Why is it better?
As @dantheman has said: those who have the most power in Steem, have the most to lose if things go wrong. This is not necessarily true in other economic systems, e.g. corporations.