The Oromo/Somali split was about 1200 AD. Sheekhs Isaak and Jeberti arrived about 1325. Aweys al Baraawe, Suufi scholar and proponent of the Cult of the Saints (d. 1909), was probably the single best educated Somali Muslim of his day, but there were still large numbers of non-Muslims in the interior, which occassioned his Jamaat and other missionary efforts. Somali Muslims remain largely uneducated in the faith to this day.
The east coast Islamic tradition in Somalia comes mostly from the Hijaz and Baghdad and arrived by ship across the Indian Ocean and the Gulf of Aden. The northern traditions, espoused most loudly by MAH. are from the Najd and came across the Red Sea. They are different.
The Saud/Wahaabbi clan are still trying to destroy the evidence and revise history, but the graves of the Prophet and Fatima remain within mosques in Medina. The Baqi cemetery has been leveled, but the Shia, Suufis and others still have maps and guard the traditional and historic sites with their memories. On an annual basis, something on the order of 300,000 people visit the tomb of Sheekh Jilani (d. 1166) in his prayer hall in Baghdad.http://en.allexperts.com/e/a/ab/abdul_qadir_jelani.htm
It is not the memory of the dead or the visitation of their graves that is new in Islam.