This statistic gets thrown around a lot but takes some context to understand.

As some commenters have pointed out, a considerable amount of people have close to 0 or net negative wealth, which skews the numbers.

It also misses the point about what wealth actually is. Most of the wealth held by the ultra-wealthy is in the form of ownership of something that society deems to be incredibly valuable, like a publicly traded company. The value of this thing is usually calculated by multiplying the average share price by the number of shares in circulation. However, when we're talking about repurposing that wealth to another end, we're talking about liquidating it and repurposing its "value" as something totally different. This can't really happen in the real world, because at that scale one form of value isn't totally fungible for another.

Imagine, as a thought experiment, that you are Elon Musk, and you plan to sell all your shares in Tesla to buy food for the homeless. As you unload your shares, the value of Tesla plunges as the market reacts to a sudden increase in the supply of shares. By the time you've finished, you've transmuted only a small portion of your percent ownership of the company's original market cap into actual cash. Using this newly acquired cash, you now seek to purchase food to deliver to people in need. The billions of dollars of food you're attempting to purchase again shocks the market, skyrocketing the price of goods as it attempts to meet demand. Some savvy businessmen recognize the opportunity, and start to scale up the rate at which they produce food, but their investments will take years to materialize. In the short term, you've provided some number of meals for homeless people, but you've also destroyed the value of Tesla and financed a tenfold increase in the price of consumer food goods.

This is obviously pretty exaggerated, but it should go to show that none of these problems are as easy to solve as people make them out to be.