They had own civilization. They lost war and were genocided out. And for the record, they had wars against themselves too, just like Europeans had wars against other Europeans.

Both slavery and territorial expansion by force were wealth builders. Both took quite a lot of time too. Both were quite barbaric from our point of view, but cruelty and violence can be wealth builder. After all, Putin is super wealthy too. Stalin ended up wealthy too. Hitler same deal. There is not much difference in there.