In a nutshell: porn rabbit hole. Generic porn into having a favourite star, into seeing her do IR, seeing more IR and getting more hooked on that and so on.
To be more in depth, my first exposure was a movie when I was about 6 but I don't think that actually did anything. Proper exposure was Tori Black and Lex Steele around 2010 when I was about 15. A few years later I was knee deep in tumblr, from porn addiction/gooning, to femdom/beta stuff and also IR ones too. These varied from gifs and clips to full blown raceplay. Then Blacked launched. All of this while I was becoming more right wing. Very potent mix indeed. A decade later from when IR properly took hold and I'm still getting off to it. Whether its just normal scenes, cuckold stuff, more extreme stuff.