I've heard about lots of really crazy German war machines, the Amerika bomber that was supposed to bombard the East seaboard from France, a giant Elephant tank killer that looks more like some kind of anti-tank sniper rifle bunker than a modern MBT, prototype jet fighters, tanks with giant rocket boosted shells... and yet when I learn about the war I don't see all these crazy contraptions all over the place, their most produced tank was the Panzer IV and America alone made 20 times as many Shermans (and I'm sure there was even more T34s) plus the Luftwaffe was basically destroyed at least by the time America was in the war.

Why was German constantly trying to invent crazy new weapons when they weren't even holding the line with what they already had? Why not focus on just streamlining production of things like the Panzer IV or the Panther or rebuilding the Luftwaffe so the Allies didn't have air supremacy?