Complex sentence: The Captain was the only survivor of his unit and thus decided to turn against his former employers, linking up with the Resistance, being accepted by his former enemies mainly through the sponsorship of General Quentin Maxis.
Split into simpler sentences: The Captain was the only survivor of his unit, and decided to turn against his former employers, linking up with the Resistance. He was accepted by his former enemies primarily through the sponsorship of General Quentin Maxis.