Complex sentence: The lack of a male heir caused him to lose motivation in promoting the imperial office as a position to be carried on by his descendants; he increasingly saw the imperial system as so inextricably linked to himself that it would not survive him.
Split into simpler sentences: The lack of a male heir caused him to lose motivation in promoting the imperial office as a position to be carried on by his descendants. He increasingly saw the imperial system as so inextricably tied to himself that it would not survive him.