Arguably the common factor with many of these individuals is their overwhelming self-regard and narcissism. There is though also an element of political nous. They unashamedly recognise and use a populist agenda which does gain traction. That populist agenda often has lies and distortions but also some kernels of truth. It cannot be entirely dismissed. They can be great campaigners, at least the first time.
But where these narcissists run into trouble is whilst that populism may win some elections its ability to then deliver proves much tougher challenge and contradictions unravel. Xi and Putin may wield almost absolute power but are increasingly stuck down a cul de sac too (which of course means they have and may lash out seeking populist distractions). The playbook then uses for why they are failing typically seeks scapegoats and conspiratorial excuses.
The other thing that seems to happen is these narcissists deep character flaws and insecurity mean they cannot govern in a stable manner. Campaigning and governing do seem to require different skills and temperament. Few are great at both.
There is perhaps something in Pareto’s Lions and Foxes theory of elite power, however of course he developed this before mass democracy. As we’ve seen in the UK recently, it may look and feel chaotic, but perhaps the fact PMs can and are changed so quickly once it’s clear they are deficient illuminates a strength not a weakness in western democracies.

At least in America, there’s a sense of nostalgia for the way things were thirty or forty years ago, hence the popularity of “Make America Great Again” and the phenomenon of Trumpism. The Democrats problem is that a significant portion of their younger generation are almost as loud and obnoxious as Trump is while hawking unappealing, negative, alarmist, and frankly preachy narratives about race, climate, gender, wealth, and everything else. They’re great at telling everyone whats wrong with America, with fossil fuels, with the world in general, but they have no actual solutions that anyone outside their ideological bubble thinks will work. Nobody in either party has a clear vision of a ‘better future’ or how we get there. Nostalgia is all either of them can come up with to sell to the people. That’s either because A.) there is no path to a better future and our civilization really is doomed and on the verge of falling apart or B.) the solutions exist but they would involve tipping over the apple carts of a lot of wealthy and powerful people who would rather drag us all into totalitarian hell before they give up their, or their family’s, wealth and power. I can’t claim to know which is true, but I know which one history suggests is more likely.