Yes, and I would even hesistate to use the word "corrupted" because it implies those liberal democracies weren't destined to fail. One thing that irks me about the use of the term "strongman" is that it is often applied equally to Josef Stalin and random idiots like Bolsonaro. If a clown like him is all it takes to destroy liberal democracy, then it is fundamentally doomed anyway, something I don't believe is the case (yet).
None of those people were elected. They came to power in coups or civil wars, and were propped up by minority elements inside or outside the country. It didn't matter whether people in Cambodia wanted an undemocratic ruler or not, because the Khmer Rouge just came out of the mountains and seized all the means of state control in the country. Even Hitler, who participated in the liberal democratic system for years, eventually realised he couldn't win and just seized control.
This is another reason why I don't like comparisons of Trump and Duterte et cetera to these 20th century autocrats. If you are talking about a population voting for a strong undemocratic leader during a crisis, then pick an example of someone who was actually elected democratically, not someone like Stalin who just sort of shuffled his way up the party apparatus after Lenin died, or Pol Pot who was propped up by the US and China.
Hitler was actually elected democratically. He tried to do a coup d'etat earlier in the century and got imprisoned for it. He took the time to reflect and figure out other means to achieve what he wanted. He then went the democratic route and got the popularity vote and became a strong undemocratic leader during a crisis.
"The votes that the Nazis received in the 1932 elections established the Nazi Party as the largest parliamentary faction of the Weimar Republic government. Hitler was appointed as Chancellor of Germany on 30 January 1933."
There are many similarities to make between Hitlers rise to power and Trumps presidency. Their rise to power, the rousing of the people, the fanatics following them, their radical, nationalist ideas and pride. Imagine how close he got on January 6th.
And there are some forms of democratic government that are dangerously undemocratic. Most West-European democracies have a multitude of parties to voice a broad spectrum of opinions from the people. Different parties fluctuate in size, depending on the wishes of the people they're representing. That way there are always 3, 4 or perhaps 5 parties necessary to have a house majority. And you need a house majority to govern succesfully. So there's always multiple parties deciding over policy. If there's only a 2 party system you take away alot of choice. Do you want either this or that, 1 or 0, black or white? There is no grey, no 0.5, no this & that. Its either / or. Which also makes it dangerous. Because the vast majority of the people is fine with whatever, just dont mess it up. But there is also a small minority that are leaning towards extremes. And with just a 2 party system that small minority can dictate and influence the future of an entire country, including that vast majority that is fine with whatever.
With a multi party system that small minority with a more extreme stance will vote for a party with a more extreme stance. That party now consists mostly of people with those beliefs. The vast majority which is fine with whatever will vote somewhere in the middle, sometimes left, sometimes right, sometimes green, sometimes economic. And sometimes all the way to the far left.
What you end up with are 3/4/5 parties that represent what the majority of the people belief and want from their government.
January 6th was a very dangerous day which could've ended up way different then we might've expected. It was a day that came extremely close to being the end of modern democracy. So I agree with you in saying that liberal democracies are corruptable, but some more then others. A lot more.