The Germans may have still had at the time a sizable army but they were emotionally defeated, no longer had the will to fight; Truman just wanted the war to be over with.
Nearly half Germany’s male population was dead, missing, or captured. They were well and truly defeated, even if on paper they were still had formidable military units. We could have given them all the ammunition and supplies they could need, but nobody could give them the kind of morale boost required. For the most part, all they wanted to do was limp home and see if their families were still alive.