Yes because the web is already a kind of knowledge graph but it's mostly written in natural language, and thus it's very hard for machines to traverse and reason about it. The Semantic Web was an attempt to formalize some ways to make the web's inherent knowledge graph nature more explicit and thus easier for programs to understand.
No, because knowledge graphs predated the web by many years and KGs are a bigger topic than just the web.
Programming languages are valued both when they reveal inevitable design, and when they enjoy widespread adoption. We continue to have many programming languages, because there is no consensus on inevitable design.
The design of "this" reveals no deep secrets about the nature of the universe; the only parts that seem inevitable are the parts that seem obvious. And all of what one sees seems obvious; the choices involve what one doesn't see, what is left out of the system.
The value here is in widespread adoption. The system is good enough that people can agree to use it.