I don't remember exactly how it happened, but I know the general trajectory.
when I was quite young I'd fap to whatever I could find, although I'm pretty sure I basically never saw interracial at this point. started with sport's illustrated's swimsuit edition, then browsing freeones for galleries, my friend's dad had a collection of porn dvds we'd watch when able, and then watching professional porn videos on xvideos on a console browser once those became a thing with wii/ps3. at that time it was just run of the mill professional porn, I remember liking gianna michaels and naomi russel (still do), and eva angelina, eve lawrence, and other chicks with fake tits I'm no longer into.
by the time I got my first computer in high school I exclusively watched pov professional porn. looking back on it, I remember lex steele basically being the only black guy with pov videos, so I just didn't see much interracial, but I don't remember actively avoiding it either. honestly no idea if I just ended up with those videos by downloading megapacks of the girls, or if I actively sought them out because I wanted more of the chicks I liked, or what.
I have my empornium account's download history to help with the last decade. up through 2014 I was still downloading pov like mompov, netvideogirls, publicagent, and the like. the obvious turning point was in late 2016 when I downloaded a rebecca dream siterip, and it's been nothing but interracial since.
clearly I was either downloading videos elsewhere or watching on streaming sites, since I think it came about much more organically than that. iirc I found myself going back to those videos with lex steele more and more, possibly noticing or feeling like the women liked fucking him more or weren't needing to act like they did with regular actors.