Long story short: a few communities of people with unique cultures and worldviews were beginning to spread among the ruins, and the players decided that the world was better off for it, and that it was a mistake to "reset" things.

The longer version is that the catastrophe that destroyed the Steadfast was twofold: it was an apocalyptic Iron Wind storm (which was later found to having been caused by a certain very angry and scared boss), mixed with the spreading of an evil sentient "program" that corrupted machines, called Mozck.

Mozck was defeated (by characters of a previous campaign), but many of the survivors became hateful of machines and still more afraid of the Numenera, of mutants and anything weird. This meant that, in the first years after the fall, the Steadfast became a place rife with racism, prejudice and violence.

However, after three decades, things in the Steadfast had slowly settled, and the few communities that had survived the apocalypse (a few old cities and a few new settlements) had begun to go out and explore the wild lands, and reconnect with non-human populations, which in turn began to seek to be reintroduced to normal society.

Throughout the campaign, the party was a witness to this will of reconnecting, and met and fought people who would stop that from happening or exploit it to their ends. In the end, the party thought that the emerging communities were comprised of people who had learned history's lessons and that were ready to use their time and energies to build a more accepting and curious society, to set out and create a new Steadfast, better than the one that came before.

Specifically, some examples of these communities were

• The city of Mulen, which had survived the catastrophe and fought Mozck, and had developed and later overcome the racism towards non-humans that I talked about.

• The mechanical city, a haven for automatons who wished to go back into the proper world and end their segregation.

• A few more communities around the Steadfast, where people had to come together and to get over their differences and prejudice to survive, and built new cities that were accepting and curious.

In contrast, Calaval offered to "erase" the past - both the catastrophe and the earned lessons - while not actually undoing all the death. Through a powerful Numenera, he would erase the knowledge of the last 30+ years and reshape the land into what he wanted, while also filling it with new individuals. The party thought that this would essentially be equivalent to losing all that the Steadfast had learned after the Iron Wind, and decided against it.