You do the same,  with what other people you relate them?. It was to prove that Dorians who came from the Epir were in reality a  Pelasgic group and other Pelasgic group lived in pocket inside Greece so they were not Greek .  At “Homer, Herodotus, and Thucydides, and were said to have inhabited various areas, such as Thrace, Argos, Crete, and Chalcidice. In the 5th century BC the surviving villages apparently preserved a common non-Greek language.”  www.britannica.com/eb/article-9058989/Pelasgi.Dodona