The correct answer to this open question is the following.
The assumptions that the author makes when presenting the information are that the author makes a comparison of what could have happened on Easter Island to other places in the world that suffered a similar fate.
There is practically no other historical data that should be considered before making such claims. Indeed, what happened on Eastern Island, also called RAPA NUI by the natives, is a mystery. Yes, there are legends and oral tradition stories that refer to what could have happened, but nothing based on scientific terms that could be demonstrated. Theories varied form the possible scenario of the sinking of the Lemurian continent. Due to that incident, many natives decided to leave and sail to other regions of the planet such as Hawaii, the Polynesian islands, and of course, Easter Island.
