IMHO, it's pretty hard for people who find no joy in having power over others (maybe because they perceive power over others as a massive responsability rather than as a consequence free ego-boost) to understand the mindset of those who derive massive personal pleasure from having such power.

Personally the way I manage to intellectually understand it (or at least think I understand it) is to imagine how it is having zero Empathy, hence not caring at all for the impact on others of one's action if said others cannot hurt you back if you hurt them. If one has such a mindset ,the power over others is never felt as a weight or a responsability, it is just a tool to at will make other provide you with some direct or indirect form of personal enjoyement - sexual pleasure being a pretty standard direct one, money being a pretty standard indirect one - hence it's logical that a person like this would seek power over those others who can fullfill their wants and which cannot or will not reciprocate if and when they hurt them.

This explains not just this situation but, for example, things like people in management positions exploiting their power for personal pleasure or simply for personal upside maximization.

Of course even somebody with just a bit of empathy cannot "get" at an emotional level such a behaviour because for them hurting others means them feeling the hurt they caused to others, hence they would feel guilt (an highy unpleasant feeling) so they refrain from acting so. That said, when "normal" people find ways to isolate themselves from said empathy (rage, anonimity, prejudiced, etc) they're still capable of horrible things exactly because no empathy = no guilt.

Anyways, that's my theory!