These people fear Somaliweyn because of what it is. Unlike Kenya and Ethiopia, multi ethnic states merged by colonisation, Somaliweyn is an ethnostate. There's no wriggle room for them to exert any influence on such a nation. Not only would they lose land, coastline and resources, the formation of the somali nation state would trigger more ethnic separatist movements. Their country is balkanised and they lose all power. At the end of the day Somalis benefit and they lose everything.