The author demonstrates how characterizations of major ideological trends of thought are largely influenced by ruling classes ("elites"). One such period called the Enlightenment, which emphasized the discoveries of the material nature of our Earth (and a little beyond), also was anathema to the rise of capitalist ruling classes.
In addition, the Enlightenment examined the old ideas of feudalism and discovered that they were full of errors like the divine right of kings, feudalism's cosmology which placed the Earth at the center of the universe, and obedience to Roman Catholicism also gave rise to a whole new range of ideas that were first dramatically expressed during the French Revolution and soon led to socialist ideas, that is, to ideas of equality of rights and opportunities among inhabitants of regions.
However, simultaneous to this, capitalist classes arose in various European countries which would soon formed ruling classes in those countries, and they saw such ideas as incompatible with their interests of private economic property and all the benefits derived from that ownership and control. They soon shaped what became known as a ideological period of Romanticism. This period was characterized not only by the mystification of nature but to differences such as language, race, and above all, nationalism that always favored the regions under the control of capitalist ruling classes.
The influence of Romanticism on politics shifted revolutionary thinking from burgeoning socialist movements to nationalism instead. Nationalism is the perfect class conciliatory ideology in that it retained the full social order/hierarchy (i.e. it includes the elites) and homogenised the people by excluding other national languages and foreign communities while putting the elites into positions of leadership and control.Now we have entered a period identified as neoliberalism (the ideology of the new capitalism) as the capitalist ruling classes have outgrown their nation-states and formed transnational capitalist ruling classes such as we see in the US/Anglo/Zionist Empire versus the rest of the world. Trump represents ideologically the earlier period of capitalism which glorified nationalism while the Deep State (see this, this, this, and this), which is in command of the Empire, pushes their neoliberal agendas under the Empire using deceptive psychological practices developed in propaganda against enemies in WWI and WWII, but this time aimed at their own populations.
Using divide and rule tactics and stirring up xenophobic attitudes and fears, the elites ran the new homogenised nations and used them for their old purposes: war. Modern global power struggles of the twentieth century started with nation set against nation in the First World War.