He did become their enemy shortly before the end of WW2.
Hence why the US took his spot. Because we were still a "newborn" country full of young, blissfully ignorant souls and had much more to offer than Germany did when it came to wreaking havoc across the world. Once Hitler began to produce results with technology FAR ahead of any other country at that time, he started to see himself as a being above all others, including those in the "Illuminati". This is when he went on his own and THEY began assisting the Allied Forces instead. This is why we saw a sudden change in the tide of the war so abruptly. Not because we were superior but because we had infinite intelligence being fed to us by THEM. Where do you think we got most of our military and weapons technology today?

The start of WW2 however, the Nazi Regime (both military and science wise) was completely funded by the "Illuminati". I put that in quotes by the way since I have no knowledge of their existence and that all I know is some force comprised of shadows does do a lot behind the curtains of it all.

This however is my personal opinion with very little proof to offer so take this all with a few grains of salt haha.