I think it's more that all the big birds the eagles hunted were hunted by humans. It wasn't just moa, the other big birds are gone too. E.g. search for New Zealand here: https://en.wikipedia.org/wiki/Island_gigantism

> Island gigantism, or insular gigantism

These are great terms. Thanks.

It's sad, but it's why most peeps over here never share the location of breeding grounds or habitats with strangers.