i'm not ever gonna run, because i don't have the charisma to succeed at it, but if i were, it would be to change things. therefore my vote. there's a lot of things going wrong, and i'd love to change it.
for people that aren't running (yet), polls like this are kind of strange. of course, i don't know the people online here that well, but from what i know (anecdotically and according to some research) most people that get into politics are motivated to change things for the better (whatever "better" entails to them). if they somehow manage to become influential enough, they'll then get swept up in bureaucracy and compromise, and some indeed start to do it primarily for power and prestige, and some go arbitrary and stop caring. (good on you for being honest amadeus ofc lol)
like, let's presume a sociopath. becoming a politician isn't really something a competent sociopath would do. the litmus test for these things is whether you can actually succeed in this manner. for every strange opportunistic demagogue, there's hundreds of people like that who, like, just went into finance, lol. it's much easier to climb the ladder and get into absurd debauchery and faux prestige if you just get rich the normal way.
it's like why people want to do art. of course ego is a huge part of it (artists usually have plenty of ego, yes), but most people don't start singing specifically to become rich & famous. it's a dream a lot of people have, non-artists in particular, that's how stuff like american idol happens. i could bend and say sure they might want to sing to become famous, but to become rich? just study marketing or finance. if you fail, you'll land a comfortable life.
failed artists - and failed politicians - spend a lot of time doing minor work because they can't help it, not because of the money and prestige. and most people that do artistry or policy aren't beyoncé or the president.
so why are politicians seemingly so corrupt and debauched? because the top sucks. to get in then, you have to be or become that kind of person. there's a lot of structural reasons as to why this happened (eg classical conservatives - like the old of 'em - thought that keeping a wealthy patrician class was the best way to preserve feudalism, and that thread has continued through governments to this day) but in the end, like, people that want power for the sake of it are usually smart enough to get a job with a better batting average.