The most frequent interpretation of Hamas, the reason that G-d declares that the earth must be wiped clean of all living things, aside from Noach and the birds, insects and animals in the ark, is robbery. The famous Gemara says that the verdict was sealed only over Gezel or theft.
The question is why was theft such an extraordinary crime that it necessitated wiping out not only mankind, but also all life on the surface, for it's explicitly stated that all life had become corrupted. Animals have no concept or legal standing when it comes to property.
Furthermore why is this suddenly an issue that had not been mentioned previously during earlier generations which did not seem to have the same crime problem?
To understand that last point, let's go back to the two earlier sins. First Adam and Chava took from the Tree of Knowledge that they had been forbidden to eat from. Second, Kayin, unlike his brother, brought a sacrifice to G-d that was not from the best and resented G-d for rejecting it and despite being warned by G-d that this would lead him to sin, went on to kill his brother over it.
What did both acts have in common? The human mission on earth, at that point, was for man to act as stewards of G-d's world, to first watch over the Garden of Eden and then to rule the animal kingdom.
Adam and Chava "stole" from G-d by taking of the Tree of Knowledge. Kayin "stole" from G-d by working the earth and refusing to properly acknowledge whose earth it was, giving G-d a share, but not the best share. Those thefts were symptomatic of a wider culture of robbery that failed to fully acknowledge G-d's mastery of the world.
That culture of robbery doomed the generation of the flood, which abused its stewardship of the earth, over its plant life and animal kingdom, to corrupt the earth by using it without acknowledging G-d or His laws. And so G-d removed them and the plant and animal life that had been within their responsibility to care for and use.
The culture of robbery led the Dor HaMabul to steal from each other, for theft from man is a sign of a lack of faith, and led them to steal crops and animals without bringing sacrifices or otherwise acknowledging Whose they were.
Noach however walked with G-d. He remained Tamim, Whole, and was therefore saved. The ark was a renewed stewardship that allowed Noach to reclaim the duties that had been assigned to Adam and his descendants. By taking the animals and then bringing them as sacrifices, Noach was granted a new covenant of human stewardship over the earth.
That is why the salvation was accomplished through the ark and Noach's task of collecting the animals made him worthy to replenish the earth.The Covenant that G-d forms after the flood is made with all life and all flesh. The covenant with animals is formed through man. When man keeps his responsibilities as steward, then the covenant with all life works through him. When he rejects it, then he steals the animals.
While G-d stated that man was likely to break this new covenant as well, He would no longer curse the earth, destroying plant and animal life because man forgot his place in the world.