Found this quote of Joseph Brodsky in my 1999 scrapbook:
People become tyrants not because they have a vocation for it, nor do they by pure chance either. If a man has such a vocation, he usually takes a shortcut and becomes a family tyrant, whereas real tyrants are known to be shy and not terribly interesting family men. The vehicle of a tyranny is a political party (or military ranks, which have a structure similar to that of a party), for in order to get to the top of something, you need to have something that has a vertical topography.
It's from some essay of his, though I've no idea which one and what volume I found it in.