The evidence is that the Gorousei are aware of that, they live in the Red Line to avoid this situation. They also probably "exterminated" the Lunarians so they can secure their own safety.
That isn't evidence.
They eliminated the Lunarians because they lived on the Red Line and they hated that because they were regarded as Gods which the Celestial Dragons believe they themselves to be.
It's a god complex they have based on what we know.
We also know they're racist, and hates every other race, and just want to rule and enslave anything they don't consider equal to them.
Doesn't necessarily have to be a goal, more like an inevitability.
Not sure what sources you've read regarding the spoilers and the summary, maybe you've only read what is here. There are other sources that translate pages of the raws which explicitly state:
Vegapunk at the start of the chapter: This video will soon connect the world together, whether by knowing it, or the inconvenience of know it...
The continuation of VP's statement is at the end of the chapter stating it concludes with the world being sunk which suggests it's a matter of knowledge that results in the world sinking from what I can gather.
We know for a fact the WG don't want people knowing the truth. Therefore, it's not inevitable because the Gorosei don't want the world to know the truth.
It's only inevitable IF the world knows the truth which is what Vegapunk just said. He said the world knowing the truth whether purposely or mistakenly will conclude with the world being sunk because the WG will:
- Kill anyone who knows anything related to the Void Century.
And in this case, it's not just anyone, it's everyone being aware of details of the Void Century, thus the metaphor of the world sinking based on what I've read from the Raw Translated pages.
It makes no sense that the Gorosei would want the world to sink when:
- Their goal is to maintain the rulership of the world... why would you want to kill slaves when you need slaves as a ruler?
- Building the Tequila Wolf which has been going on for 700 YEARS... why would they build it only for it to get destroyed? It only connects to other Islands, or rather, it will connect to other Islands.
- Right now, they're crying about Revolutionary Army cutting of food supplies... why would they want to sink the world when they need slaves for food?
Sinking the world serves no purpose based on all that's known.
It makes no sense at all.
Could well be wrong, but I'm going with this being metaphorical. Why would your goal really be to sink the world?
Rather than waste a 1,000 years sinking the world, why not just kill everyone? If sinking the world is something they want to do, it essentially means they want to make humans extinct... if that's really the goal, rather than waste time on some absurd idea to sink the world, just kill everyone.
If anything, we know for a fact that they want the Motherflame weapon which we know is pretty similar to an Ancient Weapon. The WG have been trying to get hands on Pluton which they know can destroy Islands effortlessly.
Rather, what VP is probably saying here as well is the WG want to acquire a weapon capable of destroying the world to enforce their dictatorship further than it currently is.
And for countries that do not bow down to them, they get destroyed and that will raise the sea levels like Lulusia.
Not that it's a goal.
As far as I'm concerned until more information comes, this sinking thing is hyperbole, metaphorical or just referencing the fact that nations that don't bow down to the WG will result in higher sea-levels.
They need slaves, can't have slaves without a population of people.
Can't have food without Islands all over the world to grow food and acquire resources.
I think the sinking thing is being taken too literally, that's my interpretation until otherwise proven wrong.