Master Moral Vs Slave Moral Analysis

Why does Nietzsche insist that the pleasure that comes with power is preferable to the happiness that comes with virtue and the exercise of reason?
There are many ways to approach this question and I’m not sure if my approach is correct. But I will try anyways.
If you look at the text Nietzsche stated “it needed, first, only to answer “Happiness” to the question: What do men want? (one dared not say “Power”: that would have been immoral)” (page 57) Why would “Power” be immoral? To answer this question I would have to go back to Master Moral Vs. Slave Moral. Nietzsche stated Master Moral was of “noble human being honors himself as one who is powerful, also as one who has power over himself”. (page 25 &26) And Slave Moral of “slave’s eye is not favorable to the virtues of the powerful: he is skeptical and suspicious,
(page 26) Throughout the story Nietzsche interpretation of Master Moral (a.k.a government, a.k.a political/religious leader, ext.) is skeptical and I feel he leans more to the minority. If you look at the text “Human being whose nature was still natural, barbarians in every terrible sense of the word, men of prey who were still in possession of unbroken strength of will and lust for power, hurled themselves upon weaker, more civilized, more peaceful races, perhaps traders or cattle raiser, or upon mellow old cultures whose last vitality was even then flaring up in splendid fireworks of spirit and corruption”. (pag 28 & 29) Nietzsche is trying to say that the loudest, most ruthless are the ones who survive and that is not actually a good thing. One can interpret power being immoral because as a human we should look for the urges to do kindness verses the need for power. However, I think Nietzsche is also trying to say that even if we think that we should be kind (because it is moral) most humans have the urge of seeking