I was going to ask a similar question, but you beat me to it.
I suppose that "Music of White Origin" would encompass about 99.9% of all Western music and, for that reason, some would argue that it would be unnecessary to have an organisation to promote it.
There's no cure for such ignorance.
Jazz is a genre of music that originated in African-American. Wikipedia
Rock and roll is a genre of popular music that originated and evolved in the United States primarily from a combination of African-American genres such as blues, jump blues, jazz, and gospel music. Wikipedia
Ethnomusicologist Gerhard Kubik traces the roots of many of the elements that were to develop into the blues back to the African continent, the "cradle of the blues. Wikipedia.
I could go on to cover a host of other genres. But perhaps you could do it yourself.
So, except for classical and other ethnic music such as Irish, Scottish, Breton, Folk, etc, any popular music that did not include "music of black origin" would be rather thin on the ground.
But, if that's the case, shouldn't black (and I believe that term is still an acceptable description) people feel rather patronised by a "MOBO" organisation being necessary? Surely, that would suggest that "MOBO" music is so insignificant that its promotion is essential.
Maybe, just maybe, the MOBO awards were created because black musicians were not being recognised in the existing awards, even in the categories that included "music of black origin".
So maybe, just maybe, there was an informal prejudice against black musicians which was not reflected against white musicians by the MOBO awards.
It wasn't that "black" music was or is insignificant, it certainly isn't, see my comments about origins. It was that black musicians were not being recognised. But an award for black, or white, musicians would be considered racist. So a new award was created that was not prejudiced to either white or black musicians.