If the myth resonates with people it's not difficult to install it. There are certain sign symbols an artist uses that trigger a reaction in most people, these are the ingredients to what becomes a mythology later. If you look at what the Soviet and Nazi propagandists were doing you can see the attempts to create a new myth, and it was pretty effective.

Imperialism is another "ism", an ideology. Modern ideologies don't have close parallels with the pre modern ages. It's mostly a European thing that spread with European contact, and ideologies tend to be entangled with technology, economic, political, and cultural institutions and situations.

If you're interested in a book, or e-book, check out Will Durant and the story of civilization series. It's highly accessible and despite a few issues, is still useful today. He takes a broad view of what is important and spends more time on art, ideas, and processes than battles and assassinations. The writing style is superb and uses a judicious mix of details and broad strokes (he even uses a different font size for sections that are highly specialized like currency and price overviews so it's easy to skip the uninteresting), and to this day the books give me plenty of avenues for exploration.

Critical theory isn't bad, it's useful to a point. However, when one can only find problems, meaning is going to be lacking. The ultimate flaw of the program, IMO, is that change cannot happen without understanding; understanding tends to remove the urge for change. This is why I find the critical theory aggravating, if you don't understand it, how can you know what needs to change? Most of my dislike of critical theory stems from it being too easy and mostly rather boring in the end (perspective wise I prefer interaction theory), it's exciting when young and inexperienced, but personal experience should reveal how ultimately there is no answer or solution to anything offered by critical theory, just constant flux and power dynamics and questions without resolutions. This is a very unsatisfying view of the world that lived experience puts the lie to.

Not officially, you had to be of German descent on both sides to be a member and Jews weren't allowed to be Germans through most areas.

People are all the same species. Why do beavers from different areas do the same things? Why do animals of different species and different continents do similar things in broad strokes?

As to your final question, reverse everything. Why the vast variety of differentiation in animals across the world? How have basic human needs been met with the diverse responses of humans to their needs?

I wonder why it wasn't written in Aramaic.

I was going to say kurds. Jews also have a very long history. The Egyptians do too, still using shadufs in the early twentieth century (probably still today).

People say Frederick II might have converted to Islam, I am not one but it's muddy, but he did know Arabic and the leaders he engaged to hand over Jerusalem without a fight were impressed by his knowledge of both Islam and Arab ways that he gained from his childhood in Sicily. There was some issue when later crusaders arrived in the crusader states that they had "gone native", adopting the clothing and manners of the very hot near east rather than dying of heat stroke in traditional Frankish clothing.

I think the worst colonies were purely economic in focus.

There have been attempts at starting benevolent societies on the lands of other people, tmk it hasn't worked out. The closest thing I am aware of in American history is Pennsylvania, but even they annoyed ended up cross with the native people despite their efforts. The mindset of colonization is not productive to benevolent relationships.

Muhammad. Marx may be a close second, if he hasn't already overtaken first.

Iirc, it's because of Petrarch, who was frustrated with the lack of written sources from the period. The term was also used by Voltaire for the same reason. It wasn't that dark, at least the people living during it didn't seem to think so. It's important to remember that all of those "invasions" tended to be more incremental, but by putting hard bounds on it, in our minds it comes across as German apocalypse. If you look at the sources, you find that it was even more a case of migration and attempted assimilation, hence why Germans were commanding Roman armies against other Teutonic forces. Not to stir up shit, but you can look at the current migrant issue around the world and see how people describe a rather prosaic event, with headlines like "Invasion" being popular a popular way to frame the scenario, it wasn't that different back then. No, it wasn't some collective trauma that is being referred to by "Dark Ages", just a current lack of sources. Those sources are being discovered and analyzed now and an interesting picture of an ingenious adaptation to circumstance is being developed.