When the physical world was destroyed in the mabul, it was because the people had corrupted the world internally. Noach was supposed to use the 120 years of building the teivah in order to correct the internal rotting of the world, so that it would not have to be completely wiped away. Although Noach did not succeed at this job, Avraham Avinu did—saving the world through connecting others with Hashem, and turning people toward each other favorably. The physical world comes together—or breaks apart—due to the state of the inner realms, i.e. the actions of humankind.