This vacuum pump is driven by the chain. It seized up and damaged the chain, and that threw off the valve timing.
A vacuum pump is used to create vacuum for the brake system. On modern BMW's your engine no longer creates enough vacuum to support the brake booster due to the valvetronic system. Vacuum is no longer created in the intake manifold at times and could lead to a loss of brake assist. To make sure there is enough brake assist BMW has added a vacuum pump that runs off the engine. If the vacuum pump fails it can lead to a loss of brake assist or in the worst case scenario if it seizes it can lead to engine failure.
Yikes. So it seizes, breaks the timing chain, and the pistons smash the valves at max lift. The BMW engineering analysis probably determined that driving the pump off an external aux power belt was too unreliable and risky. What a brilliant design!