The ease of which Second Coming by Mark Russell and Richard Pace extracted itself from publication from DC Comics staggered a number of industry observers. It has usually been an onerous process for a creator-owned series to leave DC Comics and find publication elsewhere, even when the publisher actively wished it gone, such as with Garth Ennis and Darick Robertson's The Boys. The deal is quite complex, allowing DC Comics rights regarding amendments, options and a general hedging of bets, even if DC choose not to publish the comic. Under normal circumstances, it could take years, and DC wanted to keep the option of publishing, many years.
I am told that the decision to make changes to comply with new standards at DC Comics, would have also affected the recent Punk Rock Jesus by Sean Murphy if it had been published now, and definitely would have stymied Preacher from the get go.
The word came from upstairs, but it was action taken by DC Comics publisher Dan DiDio that allowed the rights to revert to the creators for publication elsewhere so quickly. He was the one who told the team about even more changes that were now going to have to be imposed, but it was he who made the quick extraction, even as the comic was piling on the Advance Reorders.
The decision wasn't made because of the concern expressed by Christian conservative websites, Fox News, or Breitbart, nor the quarter-of-a-million-strong petition. But it did draw attention internally at DC Comics that might not have been drawn otherwise.
But it's also worth pointing out that such Christian commentary was not universal. Christian lifestyle magazine Relevant Magazine responded to the petition's criticism which asked what would happen if a comics company satirised Mohammed, saying,
If a satirical comic book series about another religious figure was pre-emptively canceled over backlash, the likely story would have been one about "PC culture" run amock and how "SJWs" these days just don't understand the First Amendment and the same old handwringing about snowflake millennials that has now become a tired cliche. It's very easy to tell people offended by something that doesn't offend you to just "change the channel" or "let the free market do its work." But if you suddenly start fretting about being offended as soon as the shoe is on the other foot, don't be surprised if you're accused of hypocrisy.