Final answer:
The maritime fur trade was profitable because sea otter fur was scarce in China, leading the Chinese to pay high prices for it. European merchants exploited this scarcity to establish lucrative trade routes and make significant profits.
Step-by-step explanation:
The maritime fur trade was so profitable because sea otter fur was scarce in China, so the Chinese paid high prices for it. The European merchants took advantage of this scarcity and established lucrative trade routes to supply sea otter fur to China. The high demand for sea otter fur and the scarcity of it in China allowed European merchants to make significant profits from the maritime fur trade.