If he did have plans of controlling europe or whatever why didnt he just wait it out for germany to recover from the first world war and stock up on everything war related in the mean time. IIRC he had a firm grip on germany so he shouldnt have been worried about loosing his power. Even if they started killing off jews in their own country i doubt that the rest of big powers would care enough to risk so much.
Because with every month he was losing what little advantage over the Allies he had, and because his military buildup was not sustainable in the long term.
By 1938, the Allies were rearming at a fast pace. By comparison, German military couldn't expand much more. The equipment it acquired during the 1933-1938 period, once cutting edge, now was becoming outdated. The costs of keeping the already existing military machine were staggering. Army generals (Beck, Fromm) were suggesting that the alternative was either using it in action or downsizing. From 1940 onward, Germany would need to procure equipment it didn't really need just to keep the existing armaments industry in place. Highly ambitious plans calling for the expansion of Kriegsmarine and Luftwaffe were still being announced, but had little connection to reality (e.g. the planned air fleets would require most of the World's air fuel production to function).
Sources:
Evans, Richard, The Third Reich in Power, London 2005
Tooze Adam, The Wages of Destruction, The Making and Breaking of the Nazi Economy, London 2006
Germany and The Second World War, Volume I, The Build-up of German Aggression, Oxford 2003.
As an extension, the German finance was very problematic. They needed loot. They were for example near bankrupt until they annexed Austria and got it's gold reserves.