Of course it’s a money grab. I don’t think any of these countries are interested in retribution so much as wanting to preserve their current lifestyles. Increased flooding and storms means those lifestyles become more expensive.
You know the GDP per capita in Vanuato and Tuvalu is about $3000, or roughly one tenth of the poorest US state, Mississippi?
Source: https://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&...
People can go and live in a very basic way if they like; that is on them. There are communities that do it here and there. It just doesn't look like the Tuvaluvians have made that choice, and we know the vast majority of people prefer having luxury and comfort. Tuvaluvians are probably a lot like everyone else in the world in that they want to improve their living standard by an order of magnitude rather than keep on living with basically nothing on some island somewhere.
It is easy to romanticise subsistence lifestyles but very few people voluntarily choose them when they see an alternative. The consensus position is wealth and infrastructure is the right choice. It is reasonable to assume they also want this and that their actions are generally aligned to improving their position rather than holding steady.