The difference between tyranny and democracy is that under tyranny ordinary men pretend to be monsters and under democracy monsters pretend to be ordinary men.
Power must be concentrated in the hands of a few for it to be power. Shared power is inertia, mass, nothing more. At the heart of every democracy lies a conjuring trick - true power is taken off-stage, while the illusion of power is put on display for all to see.
What makes democracy valuable is that maintaining the illusion keeps the powerful in check. The monster cannot leave his box, the puppetmaster cannot emerge from behind the curtain.
Power does not corrupt. Corruption empowers.