So why have stock prices fallen so much in the rest of the EU after Brexit?

From the Economist:

But it is a more fundamental, yet less-discussed, concern that is unsettling businessmen to the core, and not just German ones: loss of control. Without the British, they fear, the balance of power in the Brussels legislation-factory will shift to countries that favour protectionism over free trade. Bosses in every sector, from finance to pharmaceuticals, are worrying about the European regulatory climate when they can no longer count on the British banging their fist on the table, demanding free trade and lobbying for open markets. Britons at the European Commission are already being relieved of some of their duties. Over the coming months this will only get worse. . . .