There are a few diffferences


1. Nauru did it to themselves, misguided.  They never pursued advancement in education, economy, etc. etc. they just spent the money they had without thinking abuot their future. you should have seen how much they spend travelling the globe, when they dont even have proper desalination plant to provide for their population. on the other hand, what future lies when your country's riches is the land itself. Overmining would simply result to their extinction, and then what?till they are a square kilometer country ?


 


2. Qatar invested. They keep on investing. and get robbed.