What is this clear thread you speak of? The last one just doesn’t seem to belong to the others. Hitler came to power in the midst of a world-wide depression with mass unemployment when the established political order was under threat everywhere. It was a time when eugenics and ethnic hierarchies had some legitimacy in the scientific communities. No scientist or non-nihilistic energy expert today agrees with Trump’s nonsense, and the US economy is doing much better than 8 years ago by every measure.
I think you could improve the timeline by focusing more on the corporate news media, political corruption (lobbying, etc), the destruction of the social safety net by Bill Clinton and others and the rise of the anti-science movement within the Republican party.