Sadism

[Ranai]

what is the motivation behind the domination?

I think asking about a motivation is not adequate here. Motivation implies a choice.

Nobody decides to get sexually aroused by XY. It is a relation of cause and effect beyond our control. It's not a matter of choice.

For some people, domination is erotic. Being in control, calling the shots, being obeyed can work as a pleasure and a turn-on in its own right. Just as for the complement submissives, obedience to the other's instructions and submission to the other's actions causes an erotic charge, feelings of happiness, feelings of being fulfilled.

I have a motivation when I choose to do something. If people act according to their preferences, the motivation is to cause those feelings.

Some things we can influence to a degree. Among them are self-awareness, empathy and skill. (Everyone can probably add various other qualities.) I think it's a good idea to cultivate and practise them. Not least because it also has benefits for ourselves. And supports us in enjoying our many-flavoured kinks.