The reason hawiye refuse to unite is bad blood from the civil war that remains un-addressed and un-resolved, this allows for exploitation by anyone really. That is one big factor their un-resolved issues. The SNA/NISA soldiers don't trust the next soldier in the trenches thinking his working 4 shabab(that's how deep they are inside), That's why it's scary hearing SFG foolishly calling for more weapons, it will go straight into shabab hand. Even if it doesn't they will find black-market partners to upgrade thru yemen/iran and if they lose the war, they will find many willing hosts within hawiye civilians to live inside and operate an insurgency.
But there is an external actor which Somalis tend to ignore, the Ikhwan. These guys are very strong inside hawiye after they swapped with them to support hawiye only interest in Somalia and to isolate Darod and other Somalis. This happened in 1997 sal-balaar conference in cairo(ikhwan political holyland) when Aideed-Mahdi was elected President/PM, leading to the final straw in the coffin for Puntland to create it's own state.
But the brotherhood has many postures in Somalia from political parties(al ictisam, islah, damjadid and others), it has a military posture(alitihaad, shabab, hizbul islam, etc), it has an economic dimension in Bakaraha and also Bosaso, it has university posture like Simad and others plus orphanages(playin daddy for kids to brainwash new generation). Their using multi-dimensional war-front and have STATE sponsors such as qatar who hosts many terrorists such as sheikh atom, hamas, etc.
Turkey is another state sponsor under Erdogan and supports brotherhood allies in different islamic domains as they will most likely be crowned 'caliph' once various islamic theaters fall to the brotherhood. Their ultimate goal is to create a new world order based on believer/unbeliever. They will most likely be given nuclear transfer or protection by Pakistan. They will push into Europe and begin with small/weaker european nations using the same multi-dimensional posture untill they fall and transition to medium sized countries and then big countries in the west.
Hawiye and Mogadishu elites prefers to play wait/see to see a more favorable world order to emerge that will support their zero sum politics of creating winner/losers, they feel Puntland will be isolated and punished because it has been fighting them since 93(alitihaad) and hawiye friendly models such as sal balaar, north/south, centralism, political irirism etc can be achieved under a new world order that is outside the current world order of the west and it's partners such as khaleej and Puntland.
This new world order from the foreigner perspective will usher in what they want, the end-days and human rights/co-existence is removed. As for Hawiye side it's purely 'anti darod' motives.