>>9742348I liked anon's explanation that all those species are in fact alegories for cells in the body. The Matoran are something like blood cells, Toa are white cells, Skakdi are something like liver because they are probably the only sentient carnivores that serve as organic waste disposal , Vortixx would be comparable to B cells because they produce weaponry and Makuta species would be neurons that turned into cancer cells.
With Dark hunters it's complicated since about 90% of them are mutated or rebuilt beyond recognition.