That's the original tweet where Elon Musk first appeared in the conversation, as you can see the article he's replying to is where the misinformation comes in. Basically the WFP said "we can stop 42m starving for a year with $6b, which isn't a lot for someone like Elon Musk" -> CNN Business reports it as solving world hunger in general -> Elon Musk says he'll give them $6b if they openly show how they can solve world hunger. Which they obviously never claimed they could do, so when they eventually replied about how the $6b would be spent it was just ignored because it didn't solve world hunger, just temporary starvation.