I was well aware this was prior to the US entry into the war.
However, I assume the reason he was given these powers by Congress was their (accurate) awareness that the world had become a very dangerous place and the US needed to get its military act together as a precautionary measure if nothing else. Less than a year before, the US had reintroduced the draft, a much bigger imposition on personal freedom.
I’m as big a fan of freedom and free markets as anybody, but while they are wonderful things, they are no way to fight and win a war.
Thank you for the courtesy of your reply.