yeah I mean the obvious things right? the Western academic tradition it originates in only recently started becoming more diverse (+ wasn't at all in the prime of Stockhausen, GRM, etc), the technology was prohibitively rare/expensive for a long time, access to subcultural capital, market demand. if you use "experimental electronic" as description rather than genre then there's a vast, rich history of people of color, it's just almost always in service to the dancefloor, radio, whatever other medium of consumption - usually the only $ in avant-garde is jobs in academia, or if you're really fortunate composing soundtracks or something. if you go by description rather than genre then you have Patrick Adams, Roger Troutman, Juan Atkins, many many more.
there is kind of a performative circular reasoning in the production-consumption-classification of experimental electronic as thirdform means - William Onyeabor was undoubtedly making experimental electronic music but not "experimental electronic". that can shade over into actual racism (c.f. Stockhausen + African rhythms, which I too immediately thought of) but is nowadays generally the kind of relatively benign self-selection blissblogger is talking about rather than active exclusion. I do suspect the further you can go back in history the more that balance would tip toward uncomfortable racial-cultural nonsense, tho tbf there's also a long tradition of a section of the European avant-garde welcoming non-European influences.