What about Phoenician geography made them rely on imports and exports?

The Phoenicians were based on a narrow coastal strip of the Levant which gave them an excellent transcontinental position. They used their seafaring skills and created a network of colonies and trade centers across the ancient Mediterranean. Phoenician sea trade can be divided into that for its colonies and that with fellow trading civilizations. The Phoenicians not only imported what they needed and exported what they cultivated and manufactured but they could also act as middlemen traders.