What we're seeing here is a demonstration of the divorce between politicians' private beliefs and their public electoral platform, and even more problematic, a sign of the breakdown of our democratic system.
Back in the day, politicians had an idiology, and you could trust them because you knew that they really believed in what they were saying. But this started to change after the Second World War, when some politicians realized that if they believe in a minority position, they were not likely to win. So what did they do? They publicly advocated something slightly different, something slightly more likely to win, while privately holding onto their own beliefs. And then they moved a little more, because everyone is doing it and they had to get closer to that perfect center, where they could get the most votes.
Skip forward a couple of decades and what you get is a system in which the only way a politician can get into power is by outright lying about his or her beliefs. If you're honest, you probably won't get elected: there's always people out there who are just echoing focus groups. But if you're dishonest, maybe you can push through some of the things you privately believe in, without anyone noticing. Those private beliefs don't even need to be self-serving, you can genuinely believe in them being the right course of action.
So when you're a politician looking to get elected, you pick some issue you think many people feel strongly about and take a position.
Of course, the people in your focus group might change their opinions from day to day. Or maybe they're influenced by the mass media, controlled by powerful elites seeking to use the masses for their own gain. Or maybe your focus groups just aren't very representative.
Whatever the reason, something went wrong: it turns out you picked the losing (minority) side. There's an outrage, your ratings plummet, your opponents vow to enact the opposite policy. Now you can either 1) try to salvage the situation by changing your public position (but not your private beliefs), or 2) stick with your guns and not get elected for sure. Even if you're genuinely just looking to gain power to do good for the people, the only viable choice you have is is option 1.
However, this is a short term optimization. People actually do remember your promises. They hear you saying "X!" one day and "not X!" the next, again and again and again, and so they stop believing in politicians, whatever they say.
Now you've got yourself a system in which even honest politicians (the ones who never succumbed to the corrupt system) are no longer believed. All politicians are now percieved as liars, whether they are or not, and this makes the content of their proposed policies irrelevant. But people still have to vote for someone, and now the only way to win is by making yourself stand out on some other level: presentation. You have to approach the sneakiest PR firm, hire the best spin doctor, have the biggest war chest, get the best television ads, and then maybe you can win by deceiving enough people into voting for you. This is the dominant approach in the Anglosphere, where the difference between 'winning' and 'losing' is a gaping chasm, and where buying influence is both easier and more widely accepted.
If your political system isn't so conducive to manipulation by the raw power of money, that's not very effective. Thankfully, people are still willing to vote for someone they think is just like them. So they vote for the person who has a real talent for public speaking, who identifies popular grievances, but who very much is not a politician. But politics is contagious: when you get elected, you can't help it, you become a politician. You get infected by it, and by all of its associations. And thus you fall out of favour with the people who elected you, and the cycle begins again. This is a type of populism that's common in continental Europe, because coalition governments mean that you don't have to get an absolute majority to gain political power.
And this has had an effect on the established political parties too. Politics is now just a career in which the issues are no longer so important, a politician can always implement a couple of policies that benefit a certain powerful group. You might even delude yourself into truly believing that what you're doing is right. In return, that powerful group will give you a 6 or 7 figure job when you leave politics. Maybe couple of positions on the boards of large corporations, or a lobbying position, to make use of your political contacts.
This is a vicious cycle, where each of the effects is another cause exacerbating the problem. I chose to start at a certain piece of this whole mess because it fit well with what's happening in Australia now, but you might as well start at the corrupting effect of the mass media, or at the rise of the focus group, or anywhere else.
I guess this is where I should be coming up with a simple and straightforward solution. Sorry about that.