Brexit was founded on the misunderstanding that it was "faceless unelected bureaucrats" that run the EU. I'd argue Britons wielded more power than most others in the EU, and that the EU parliament is quite a lot more democratic than the British one. The british are now stuck with the UK parliament without adult supervision.
Because they still had exactly the same power in their own government, and a sizable chunk of power in the European one. Now they'll follow a huge part of European regulations to be able to trade, but have no seat at the table.