From about 750 BCE to 3rd century CE, the Crimean peninsula was invaded and settled by Schytians/Sarmatians, an Iranic grop who held a vast territory from present-day Ukraine to Central Asia and the northwestern corner of the Indian subcontinent.
What POD(s) should be needed to make Crimea remained predominantly/dominantly Scythian in language and culture, with possible assimilation of invaders during the Migration Era (including Alans from the Caucasus).