The more you look into it, the more Sudan really does seem like a place that almost seems to have been subjected to a hamfisted effort by OTL's author to justify why he's having the 'famously unconquerable' nation remain under outside rule until the 50s.
'But what about Funj? Oh massive civil war earlier than the historic crisis that leaves the capital in ruins, the nation divided and the government willing to just give up rather than fight. What about Sultan Ahmad? Manages a temporary success then dies. What about the lack of British interest? Oh Gordon gets redirected at the last moment purely to get killed.' and so on.
There's probably a world where Egypt, Sudan and Ethiopia are three rival independent native Kingdoms vying for supremacy between eachother and being played off by the Europeans during the early 20th Century.