The phrase "it falls into history in order to come back to itself" is an example of personification: the spirit or humanity's geist is also called the zeitgeist:
The Zeitgeist (spirit of the age or spirit of the time) is the intellectual fashion or dominant school of thought that typifies and influences the culture of a particular period in time.
This zeitgeist is treated as a person who "falls into history", which we can consider in context to mean something like "goes somewhere". It does so to "go back to itself", which is suggestive of finding oneself. Here's a link about the latter from someone's personal experience (found at random on the web), and here's a more dispassionate write-up about an identity crisis.
The term "in order to" is a statement of purpose. With reference to the zeitgeist, it's simply an observation of apparent intention - like that of a plastic bag 'trying' to catch leaves (another random internet link).
Putting all this together, the sentence says that at first observation, the zeitgeist wasn't well understood. After some time (i.e. after going through some history), people began to study it, and it was then better understood.
In your first quote, this better understanding is what enabled people to "find a plausible answer to these questions".
In your second quote, the people referred to as "they" appear to have a different explanation for the phenomenon, discounting the validity or effectiveness of the personification-based explanation.