summer nights talking about leaving town
Steven: The Diamonds are back?! What are we going to do!?
Greg:


LOOK AT HIM
Did…did this actually just happen. Ladies and gentlemen blue diamond just got a dorito to the face.

“How did you even survive? We blasted the planet and obliterated every gem on its surface…”
Blue (and supposedly Yellow as well) genuinely assumed before all of this that they destroyed all gems on Earth. In that case, it’s possible that they’d had to levy attacks like this before- and they worked exactly like that.
So why, then, DID the gems survive in a corrupted state instead of perishing at the diamonds’ hands? The answer, I propose, is simple.
Rose- being a diamond herself, and constantly expressing life giving ability throughout the series- protected them from complete destruction.

She could only fully save Pearl and Garnet behind her shield, but I propose that somehow, she managed to counteract White, Blue, and Yellow’s attack enough with her power that the gems on Earth were only corrupted, not destroyed. Rose never told the others about this, however- she knew what the diamonds were trying to do and knew that by all means, every gem on this planet should have died- but she let them believe that their final attack was the corruption.
And from there, what then? Then Rose Quartz makes it her mission to round up all the gems she can. Poof them. Contain them. Try to see if she can find a way to reverse the damage the diamonds wrought. Perhaps there’s still a way she can save all of the Crystal Gems…