It seems like you have the order of things mixed up. The point is that destroying a financial hub of the world is a more effective way of collapsing civilization than destroying a port.
2. Food and manufacturing nowadays depends on things like futures contracts, foreign currency exchange, lines of credit and so on. Not to mention the ownership of the companies doing it! The right type of damage to the financial system could be very impactful.
3. There’s plenty of bombs to go around.