Every people wants to magnify the importance of their own culture.
Russians used to deny that their country was founded by Swedish Vikings. Germans used to believe that the Aryans had originated in Germany. Hindu nationalists believe that the ancient Aryans originated in India. Some American Indians believe that there ancestors have occupied the same land eternally. In the same vein, some Irish nationalists believe that Kelts have lived in Ireland for many thousands of years, in spite of overwhelming evidence that this is not true.