Complex sentence: The administrative historian T. F. Tout speculated that a reason for the Wardrobe's increasing influence was its "new and elastic" nature: it was not hidebound by restrictive traditions or customary ways of working.
Split into simpler sentences: The administrative historian T. F. Tout speculated that a reason for the Wardrobe's increasing influence was its "new and elastic" nature. It was not hidebound by restrictive traditions or customary ways of working.