In the article it’s noted that the digital camera couldn’t handle the fine dust and sand of Sudan, whereas the film camera did. Are there digital cameras can handle such difficult environmental conditions?
I don't think it was so much the film vs digital, as the two aren't that different (digital has a sensor and no motor/film roll, but they're otherwise pretty much the same). The Mamiya must have just had better weather sealing, being a much more expensive camera.
Depends a _lot_ on the specific camera (and lens). Pro SLR lenses and bodies are generally more effectively sealed than consumer equipment, and generally more robust. A Nikon D5 with a well sealed prime lens will stand up to an awful lot of mistreatment. More, in fact, than the Mamiya he used.
However, medium format cameras are the best you can get for still image quality while still having something you can reasonably call "handheld", which is likely why he chose one. Also, this Mamiya (like most film MF cameras) is massively cheaper than a nikon d5, which means you care less about risk from dust damage etc.
Fuji's has one of the best weather-sealing (dust & rain) in the mirrorless segment. No idea about the lens he used, but my X-Pro2 survived (rain & snow) storms, even with a non-tropicalized lens.