For that it could be anywhere near to be feasible it would be needed to be placed in a ATL that should be even before of the WWI would be more advanced than OTL at the same point but that and supposing that said TL would follow a similar socio-politically development than OTL. It would be required that before, during and after the WWII, the scientific research and development would follow an intensely accelerated path. Given that would be needed greater theorical and practical advances/breakthroughs in the comprehension and understanding of some key biological process in general but particularly in the embryology, genetic fields but also in the Physics and Chemistry. Chiefly, on both theorical and electrical engineering and electrochemistry so as well as their practical applications. Cause for at least, that a cloning attempt could be considered theoretically, first would be needed to have firm theoretical basis and 'd have developed/mastered the, in Lab
DNA/RNA recombination technology and have designed/built and/or
available the key equipment such as, among other, a Lab adapted electrofusion machine, cryofreezing production/storage facilities, an inverted microscope (with high quality micromanipulator).
zWell,even if the whole ploty wouldn't not to fail when the 'planted' Clones would fail when they 'd be first noticed/recognized for their 'extreme' resemblance to the Nazi Germany leader. Also, It shows that the whole project/scheme was based on their blind belief in the
'Great Man (Historical) Theory of the Leadership'. One which would be needed to work in the real life which it doesn't... Cause that for that the clones would have any even with the clones raised and supported by followers sleeping cells deeply infiltrated in the host countries societies and governments