Not that it matters who the wealthiest person on earth is, but western capitalists have a small fraction of the wealth that people like Putin and Xi have.
Where do you get small fraction? That's not true at all. I can't even see either of your examples as having more, let alone a multiple.
Anyway, the wealthiest western capitalists aren't even accounted for. "author Malcolm Gladwell estimated the value of Rockefeller's fortune at its peak, in today's dollars, at $318.3 billion" [2] It's divided among the family at this point though of course.
But of the living individuals that we know (Bezos/Gates/Musk/Zuck), and have accurate info for, your statement is not true.
[1] https://money.com/vladimir-putin-net-worth/
[2] https://www.foxbusiness.com/markets/how-rich-is-the-rockefel...
In 2015, the richest western capitalist was Gates with $80b[2], which means Putin was worth 2.5x more than Gates.
Another example of how these kleptocracies tend to funnel wealth up into the top is Kadafi, who was estimated to have died with $200b stashed around the world[3]. At that time, Bill Gates was worth $61b[4].
Without proof, I grant that you can believe whatever you want about Xi. But you can believe he's a unique benevolent snowflake in the history of totalitarians, or you can believe he's just like the rest. I'm going to assume he's like the rest and wait for proof that shows the opposite.
[1] https://cnnpressroom.blogs.cnn.com/2015/02/15/putins-net-wor...
[2] https://www.forbes.com/sites/chasewithorn/2015/03/02/forbes-...
[3] https://www.latimes.com/nation/la-xpm-2011-oct-21-la-fg-kada...
[4] https://www.forbes.com/sites/luisakroll/2012/03/07/forbes-wo...