Because it works 😕

I believe that the effective growth of this kind of stuff, coupled with the decay of "objective" journalism whatever its significant faults might have been, is behind the surge in authoritarianism worldwide in places that used to be democracies. Reduced to the core, the price of a machine that turns money into public opinion has been going down, down, down, to the point where all you need is like 30-40 people working 40 hours a week at it, in order to create a significant change in electoral results anywhere in the world you'd like to create one.