You're asking the wrong question. The right question is, why is there nothing else but poverty and malnutrition everywhere but in the western world? The answer: because in non-western societies, nobody has any incentive to create a lot of wealth, so they don't.
In other words, the problem is not that there are some people in the western world who are poor and malnourished. The problem is that the western world is the only part of the world that has a significant number of people who are not poor and malnourished. If the rest of the world would stop chasing after leftist chimeras and adopt neoliberal capitalism, they could create a lot of wealth too. The western world is way, way ahead in bringing people out of poverty and malnutrition.
This is ahistorical nonsense. The west industrialized hundreds of years ahead of the rest of the world and spent a century and a half plundering the global south. Regardless, China has managed to almost eliminate extreme poverty and hunger despite following a model very different than neoliberial Capitalism. As was the Soviet Union. Not defending these regimes, just stating a fact.
The majority of the world does follow neoliberial Capitalism and has for decades. And it has totally failed to reduce poverty. Almost all global poverty reduction since the 70s has taken place in China.
You also neglect the role of imperialism. The west has acquired much of its wealth through exploitation of the global south. So of course they are wealthier, because they have stolen wealth from everyone else, trapping countries in debt or dependence and overthrowing any regime that challenges neoliberial rule. Leftist regimes have done phenomenally well given the global economic context they live within -- Cuba has a similar life expectancy rate to the United States and phenomenally low malnutrition among developing Nations. China and Vietnam have experienced staggering economic growth for decades. Just compare India and China in this regard -- a country totally dominated by Western imperialism vs a left wing government that managed to forge its own development path
In other words, the problem is not that there are some people in the western world who are poor and malnourished. The problem is that the western world is the only part of the world that has a significant number of people who are not poor and malnourished. If the rest of the world would stop chasing after leftist chimeras and adopt neoliberal capitalism, they could create a lot of wealth too. The western world is way, way ahead in bringing people out of poverty and malnutrition.