At the end of the 13th Century the Ottoman Empire was formed. At its peak in 1683 (not so long ago) it encompassed the Mediterranean coast from Algeria to the Adriatic, including all of Hungary, Central Europe, Greece, Ukraine up to the Gates of Kiev, the Black Sea (all of it), the Middle East from Iraq to Egypt, all of Lower Egypt (the North part but lower on the Nile because it runs backwards), and the Holy (at least to Muslims) Jewels of Mecca and Medina. They claimed the Caliphate (Military/Political/Religious leader of all Muslims, like the Pope but bigger and with better Armies) as early as Murad I (1362 to 1389) but it was solidified in 1517 when they captured the competing Caliph, Al-Mutawakkil III, in Cairo during their conquest of Egypt. Surrender of Mecca and Medina soon followed.
Interesting Historical trivia- until May 29, 1453 the Roman Empire (at least the Eastern part) still existed. Then Sultan Mehmed captured Constantinople which was considered impregnable. In 39 years Cristobal Colon would “discover” America (an appropriate designation in this context). As I say, not so long ago.
After The Great War (1914 – 18) the victors chopped it up and the Empire lost all the Levant and its control of Mecca and Medina. The Sultans were deposed and replaced by a secular Constitutional government led by war hero Kemal Ataturk.
On the other side of the Tigris and Euphrates River Valley was another, older, Empire- the Persians. You remember them- Xerxes, Thermopylae, Darius. That all happened starting about 499 Before the Common Era (the larger the date the more back it goes) so they’d been around more than a Thousand Years before the Ottomans were a twinkle in their Daddy’s eye. During the Great Muslim Civil War that happened after the death of Muhammed the Prophet (632 CE) they backed the actual descendents of Muhammed (Shia) rather than Abu Bakr (Sunni).
There is no God but God and Muhammed is his Prophet.
So that’s been going on for about 1400 years, in recent times the House of Saud, granted control of the Holy Jewels of Mecca and Medina for co-operating with the British and T.E. Lawrence in The Great War, and a whole lot of desert that just happened to be sitting on a huge pool of Oil, has decided to create their own Empire by exporting Fundamentalist Wahhabism (more Sunni than Sunni) and the aforementioned Oil, and importing good old U.S. Dollars and Weapons which they park in the desert in vast numbers because they can’t find enough Saudis to crew them.
Besides, Terrorism is so much cheaper.
The Meta Game that you’re watching in the Khashoggi murder is Turkey getting back in the mix. Erdoğan imagines himself a modern Suleiman the Magnificent and he’s as Muslim as Abu Bakr so- why not? The Iranians are grateful for the help, the enemy of my enemy is my friend. The House of Saud has no friends, only people who want Oil.
Hope this helps you understand the situation.