What's wrong with the sentence "the vast number of young people have launched a beautiful wind of youth to us"

Expansion is wrong. The sentence "the vast number of young people have shown us their youthful and beautiful style" is wrong. Changing "expansion" to "display" (or "display") is a verb-object collocation error. Verb-object collocation is the object of verb plus action. There are compound words and phrases, all of which are transitive verbs and nouns, and the object of verb-object phrases can also be pronouns.