Present Agews may retain the culture of the predecessors but they have significant Semitic ancestry just like Habesha.You're issue is looking at things backward, Ethiopia colonised cushite Agaws not the other way around. Its like saying Turkish people were invaded by Anatolians, the vast majority of their DNA and culture was Cushitic until the recent Solomonic dynasty
When the Anglo-Saxons invaded England they brought the Germanic language and mixed but there's still pockets of Celtic culture and language like Welsh.