Somalia was already partially controlled by the decendents of Yekuno Amlak. The royal family in charge of that area was already Christian!
It doesn't need European culture, just the looks. If you have some remnants of the Crusader States fleeing (say they got separated from the Jersuseum forces), they would adopt customs in the South. But if they are fleeing, then they're nobodies, and commoners don't get to interact with royalty.
So we need some way to get some of the Europeans South and their decedents to become in favor. I can't see this to happen with a Third Crusade POD. I can see it with PODs in the Dark Ages, but 1190 seems too late. Anyone have any creative ideas.
Yekuno Amlak reigned in the late 1200's and he was of the Zagwe dynasty claiming to come form the line of Solomon and inheritors of Axum, but in reality they were Agew ethnic group a cushtic groups that made up a part of Axum but never ruled. Geographically they were from the northern highlands around gondar.
The Zagwe evolved into the Amharic ethnic group which came to dominate Ethiopia and create an empire,
but during yekuno amlak they were over 1500KM from the nearest somali settlement.
Right next to the zagwe was Shoa an Islamic Emirate that had a muslim nobility but was multi ethnic and majority of the subjects were Waaqists.
Between Shoa and today's political border of Somalia were nearly a dozen city states and ethnic groups, mostly muslim highly urbanized and sophisticated compared to "Ethiopians", but weak and divided and not militaristic.
During yekuno amlaks reign a 300 year war between muslims and Christians started with the Muslims on the losing end for most of the time.
The Zagwe were militaristic and aggressive and started by conquering Shoa, and gobbling up city state one by one or vassalizing the larger ones.
The remaining states coalsed into the Sultanate of Ifat, when an arab hashimite family from Ziela (Wali asma Dysnasty) todays Somalia Launched a call to jihad, attracted Nomadic Somali and Afar with their large cavalry armies
and over a thousad arabs from yemen.
For over 30 years the border between Ifat and Zagwe stabalized but their were skirmishes and a cold war, till war started again and the Christians were victories again due to the King Amde Seyon (Pillar of Zion ??) being a millitary genius. Ifat lost more land and was made to pay tribute. Amde seyon also raided deep into Ifat past its borders to the east and looted, burnt Somali Cities like Amoud the source of Ifats manpower.
In written down Chronicles celebrating Amde seyons victory, he lists the states and tribes he has defeated
and this is the first recorded mention of name Somali, AD 1342.
So no Somalia was never christian and never ruled by Ethiopian, and the first time an Ethiopian army ever set foot on somali land was decades after yenkuno amlak in the 1340's.
If you go back 1000 years Axum did control the northern Somali coast as it was a maritime power focused on the navy and control of trade.
Zeila and Berbera were outposts and the population might have been christian there are ancient tombs with Crucifixes but the majority of the population were camel herding nomads in the interior.
During the Axum - Sassanid war, the persians defeated Axum in Yemen, and then briefly held ziela and berbera in 575 AD, Prophet Muhamed was a 4 year old at that time.
Residents of Ziela were one of the first Muslims in the World, there are 2 mosques with 2 qiblas, one facing jerusalem and the other mecca , the other is in Eritrea . Most likely built before mecca was muslim and arabia unified under islam. Ziela was also multi ethnic and multi faith, a christian community survived for centuries and there is a ruin of a hindu temple.