[1] http://www.merriam-webster.com/dictionary/manifest%20destiny
> In the 19th century, manifest destiny was a widely held belief in the United States that its settlers were destined to expand across North America. There are three basic themes to manifest destiny:
The special virtues of the American people and their institutions
The mission of the United States to redeem and remake the west in the image of agrarian America
An irresistible destiny to accomplish this essential duty
Sometimes it is blatant. See Congo Free State. The nominal justification was to bring civilisation and thus improve lives. Instead the people were enslaved in a state owned and controlled by private enterprise.
https://en.wikipedia.org/wiki/Rain_follows_the_plow
This led to people settling in unwise places. And you know what, even though the Wikipedia page says that climatologists now regard this as mere superstition, these areas of the US are now well-populated: A critical mass did settle, so in a way it's all worked out.
Sounds like a classic case of survivor bias though? Where would Chicago be today if it wasn't for the trains? What would be the state of Phoenix Arizona if not for things like CAP? https://en.wikipedia.org/wiki/Central_Arizona_Project
You mentioned this but I wanted to spell it out.
Or in another sense; because it exists, then it exists only for them. It ties into their earlier religion where they warped the belief that an entity called God created the world for mankind and humans, where they only reason and believe that only they themselves to be human and man.