I would venture that Cameroon, and Kenya too, wants Canada to lead the investigation because the Canadians conducted the Abidjan enquiry, and nothing came out for years.
That's probably what they are counting on. After all, the priority here as far as Cameroon CAA, Kenya CAA, KQ and the respective governments is the same. If any egregious mistakes were made they must remain secret, at least for as long as possible. The causes of the Abdijan crash were well obscured, greatly delayed and no official report was ever published. That's what they will be hoping for this time.
Can the NTSB be relied upon to keep schtumm? I think the Africans think not. They have this terrible habit of getting "lessons learned" out to all and sundry. Cameroon and Kenya will unite to prevent this.
Neutrality, my shiny metal butt!!