Europeans believed that when natural disasters like earthquakes occurred, the cause was

Europeans believed that when natural disasters like earthquakes occurred, the cause was: supernatural 

That era and lifestyle was really defined by the rise and wane in the demand for fur products, particularly hats.

Explanation:
The economic factor of life affect everyone in the same way. When demand for a product increases it motivated efforts for further supply. Scarcity of a resource will also drive efforts to secure more of it. Thus, the entire development of the "Mountain Man" was based initially on a particular market supply-demand issue.
Everything else that they are known for is primarily a result of simply surviving in order to fill their particular market niche. In daily life they often "lived off the land", which meant a cycle of deprivation and plenty.