it was a well-known license affordable enough for thirdie tv channels, and a longrunner meaning that it'd fill plenty of their schedule
it is american blacks the ones innerly drawn to it, and it has more to do with their unability to adapt to western society that they seek eastern cultural products more. As for the violence let's be real here, similarly "violent" media like Call of Duty exist and the average player is pictured as a white suburban kid. Rather than race or even "violence" this has more to do with the power-play this shonen power-structure formula DB represents, with a fixation in training and labeling etc at the expense of other developments, or calls for "saving the people of X world", the sharp good vs evil contrast; easy to project a quasi militaristic tone which is so ingrained in burger cultural expressions of all strata, and by extention their culturecucked countries of japan and fake korea.
in yurop for example other shows like one piece and naruto are sizeably larger, and casually they have a more laid-back tone classical adventure approach to shonen (sp. One piece) with character interaction happenning (ideally) more in harmony with their surroundings in contrast to the get-it-done DB way. And if not just compare the clumsy personality of Luffy with good boy Goku or the more underdog focus of Naruto with the way Goku was cracking skulls since virtually the beginning, make your own assessments
and this is not to shit on DB itself, i actually enjoyed it growing up and find its phenomenon interesting for these reasons