Short answers, pulled from the story.
Spartan poets like Tyrtaeus claimed that Dorians arrived from central Greece to conquer the Peloponnese. They stated these newcomers were led by descendants of Heracles and received land from Zeus and Hera.
Karl Otfried Müller published The Dorians on the 1st of January 1824. He proposed that northern Indo-European peoples invaded Greece and destroyed Mycenaean palaces during this period.
Nazi leaders portrayed Dorians as fearless Aryan conquerors to justify Prussian militarism. Adolf Hitler stated his belief that the Aryan race reached its apogee through invading Greece and Italy in February 1941.
Michael Ventris successfully translated Linear B tablets from Pylos written in Greek on the 1st of May 1952. This discovery proved that Greek had been spoken in the Peloponnese since the Bronze Age, undermining the core assumption that a later invasion introduced the language.
Archaeological evidence showed cultural innovations like iron-working and Geometric pottery predated palace destructions. Excavations at Tiryns by Klaus Kilian in 1978 revealed Handmade Burnished Ware predating site destruction.
By the 1st of January 1990, the Dorian invasion was considered a myth by most scholars in the field. Oliver Dickinson wrote that these myths likely had little relevance to actual historical events.