I have always shared Hegel's dialectic of the master-slave relationship for understanding dominance with relationships. That may be a good starting place and then some may disagree. Bear in mind historically not all slave owners were inhumane and greedy with presenting care, although there was a dominant position and slavery was traditional. (I am thinking of Biblical history and Greek history)
I feel there is a difference between dominance and dominant. Dominant does not have to mean having dominance, in my humble view. As shared with the introduction some cultures with 'traditional' marriage have an instituted dominant partner of position. That is cultural and not necessarily of all relationships in a marriage. Some cultures are patriarchal and some matriarchal. At times that difference is focused only within the coupling.
Treating a partner by dominating or exercising dominance is entirely different than to have a dominant position. The dominant position must be defined. As suggested dominating is a behavior worth scrutiny.
EX: (This centers on dominance with money and position) Working within the auto industry for many years I can attest many times the traditional dominant person - male or husband, (that being over twenty years back through today with personal experience), of the relationship did authorize the work. However, many, many times it was with a nod of approval from the other partner.
Many times when the lesser of the traditional partnership, female or wife, was authorizing the work as the dominant position of the transaction a phone call was made first. Who knows the what of that conversation.
I have heard countless times "She won't let me spend that much" when presenting a solution for driving needs giving cause someone or persons established an amount first. When I heard that statement I heard respect of a position by a position.
This does not answer the question of 'why' does dominance have such an effect on a person's mind. My best guess is even with brain washing techniques thoughts are still free and can be exercised with liberty. The consequence of acting upon those thoughts, in my humble view, are what weigh upon the person's mind. Feelings of insecurity, even though of being the dominant position, and behavior is a key to scrutinize both sides of that fence I would think.