Complex sentence: The Qing administration initially tolerated opium importation because it created an indirect tax on Chinese subjects, while allowing the British to double tea exports from China to England, thereby profiting the monopoly on tea exports held by the Qing imperial treasury and its agents.
Split into simpler sentences: The Qing administration initially tolerated opium importation because it created an indirect tax on Chinese subjects. This policy allowed the British to double tea exports from China to England, thereby profiting the Qing monopoly on tea exports held by the imperial treasury and its agents.