Why do you think Yemen could/can be the regional superpower? It has barely any energy resources.
As I've noted above, Yemen's civil war didn't begin in the last decade, it began during the Cold War. As did Somalia's.
Both Yemen and Somalia are located in the Gulf of Aden, the most important shipping route in the world. Yemenis and Somalis were also seafaring people who traded all across the Indo-Pacific. Yet today they don't even have navies. Instead, Somalia's coasts are illegally fished by their neighbors and foreign companies use it to dump waste illegally.
Yemen's neighbors (KSA, UAE, GCC) and Somalia's neighbors (Ethiopia, Kenya) do NOT want it to be stable. That is why every time they achieve stability, they either invade or back one side against the other. And they will literally switch sides per convenience. The people who came into power in Somalia under the AU are the same people who were running the Islamic Courts Union (ICU) minus Al-Shabab, whom the AU toppled. In Yemen, KSA has literally switched between Saleh multiple times. And UAE and KSA even supported opposing forces. They also went from pro-Zaydi monarchy during Cold War to now anti-Zaydi.
Yemen and Somalia are victims of their location, much like Afghanistan is at the crossroads of Central/South/West Asia. The pair should be profiting from all this shipping trade between Asia and Europe, and Asia and West Africa, and Europe and East Africa. Instead they get nothing and are labeled as pirates in their own waters.
Yemen was a kingdom for thousands of years, even before Islam. While the Hejaz region was minor city-states or nothing at all. Human civilization forms around fresh water, not desert (rivers like Indus, Yellow, Tigres, Euphretes, Nile, etc). It's what causes a populace to engage in agriculture, which becomes a settlement, which develops into civilization.
Yemen alone, even with war, has over 30 million people. The rest of the GCC states combined have LESS than 30 million
citizens (20 mill of which are Saudi). They are artificial civilizations.
This is simply history, biology and sociology. It was Yemeni missionaries who first spread Islam to Southeast Asia, and even the Somalis spread Islam to Maldives. They were seafaring merchants. Resources isn't just oil. That's a modern discovery. They had fresh water, grasslands and mountains for agriculture and cities, and they had a strategic port location. None of the East Arabian states have strategic location, they are in a maritime deadend zone and they are deserts. Hydrocarbons is their only claim to fame.
Think of Singapore's strategic location. That is what Yemen and Somalia is. Except its history goes deeper and wider. Singapore was always just a small city-state, whereas Yemen was a large kingdom and Somalia was several large city-states.
People don't understand KSA and UAE's foreign policy is very much intertwined with historical considerations. From the 830s to the early 1900s (WW1), the region of West Asia was almost exclusively ruled by Iranic and Turkic dynasties. And Yemen was a major civilization even before Islam, let alone before oil. That is why they posses immense fear and suspicion towards Iran, Turkey and Yemen alike.
Where you see a cultural war of civilizations, they see a genetic war of civilizations.