Also, for those HN-ers who want to really get a good, more truthful look at the causes behind WW2 I heartily recommend Ernst Nolte's "European Civil War". From the wiki page (https://en.wikipedia.org/wiki/Ernst_Nolte):
> Nolte contends that the great decisive event of the 20th century was the Russian Revolution of 1917, which plunged all of Europe into a long-simmering civil war that lasted until 1945. To Nolte, fascism, communism's twin, arose as a desperate response by the threatened middle classes of Europe to what Nolte has often called the “Bolshevik peril”.
You should be able to understand that it's a hypothesis you find convincing without evangelizing it as "truthful."
This was never the case for me. When I learned trig ratios, I always understood some basic things that trig ratios could be used for. The teacher always introduced some applications, we always had a lot of word problems, and I could fill in the gaps myself.
Same for calculus. When I learned calculus, I always understood some things that calculus could be used for.
So I understood how those things could be applied to general, everyday sorts of problems. What was missing, though, was that I had nothing to which I could apply those techniques, besides homework.
Learning math (and reading STEM papers) has become easier for me since I now have actual problems to solve. Don't get me wrong: I'm not solving particularly challenging problems or using particularly advanced math. Nothing that tens of thousands of people haven't done before me. But I do need to understand the problems, solutions, and some of the context in order to successfully implement them. This provides a motivation that was always missing before.
I suspect this general narrative is true for a lot of people: that having an actual problem to solve is almost necessary to get a student to really learn the material, instead of just coasting along for a grade.