Every other awards are not exclusively MOBO awards - I think that's the best way to put it. Privilege blinds us to the discrimination that occurs - If you look back at any awards across any media (film, tv, music etc.) that does not specifically focus on one group by colour, gender, race or religion - it has overwhelmingly favoured white, middle-class, western winners. Most of the judges have been from this group, most of the air/screentime has favoured this, and thus it favours these winners.
If someone looks at the MOBOs and thinks 'where did all this music come from?' then that's the result of all of the above. It's always been there, but it has to meet higher expectations to compete. It's partly why Adele was complaining that Beyoncé ought to have won the Best Album Grammy (partly self-deprecating modesty too I imagine).