WWII demonstrated wars of conquest don't work in the industrial age. When America and its Department of War and Navy were founded, invasion and conquest could still be done profitably. WWII showed that was no longer true–industrial machinery and skilled workers are destroyed by invasion and even base resources quickly become useless when surrounded by people who hate you. (Nuclear weapons sealed the equation.)
The Americans who fought in WWII saw that lesson firsthand and seem to have genuinely pivoted away from wars of conquest and annexation towards something closer to status quo preservation. We, of course, still went to war. But it was generally to help the current leader repel something or the other. The case in point for this is the truly devilish stuff having been shifted to the CIA's clandestine portfolio.
Renaming the DoD the DoW basically says all that clandestine stuff wasn't shameful, it's good. It's a real message being written by idiots who don't know history or war and are mastered by their own insecurities.