Based in my limited understanding of psychology, it’s about role reversal. Meaning, they are in a position which gives them quite a bit of control in their day-to-day life. This is why in the show Billions, the DA of NYC is into BDSM. He has a level of control over others that’s quite immense. This over time leads to him enjoying being taken advantage of in the bedroom. But again, I’ve only studied a limited amount of psychology, and the rationale behind each person’s choice to be dominated will have some variation, as it’s psychological. But this is the general idea behind the Dom/Sub preference.