Let me toss this one out. A figure little known in the West
Mirwas Hotak started a string of disasters that shattered Iran. By the early 18th century Iran was a stable prosperous society, Their trade and diplomatic relations with Europe were growing and the Shahs saw the West as a counterbalance to the Ottomans. Iran was properous, pragmatic, and functional. Mirwas destroyed that in a vain attempt to conqure Iran.
Remove Mirwas from history and maybe a stronger Iran modernises in the same way Japan did. Which would radically alter the whole Islamic world. Make Mirwas and his son's attacks on Iran more devestating and maybe Iran breaks up with the southern coast landing in the British Raj and the Northern and central regions falling to Russia. This would likely cause the
The Great Game to become a late Victorian World War.