Your question includes some mistakes.
First, propositions should only express beliefs. When there is no belief, there should be no proposition. But the diagram shows that some propositions are not beliefs.
This is wrong. It is common to put a whole load of facts into a computer program and to let it work out many complicated implications of those facts that people want to use but not to work out. Indeed, the person might not even want to know those implications. He might design another program to take the output of the first program and follow a routine for fixing the problem without him ever knowing the specifics of the problem. Also a lot of stuff in books isn't believed by anyone because the point of writing it down in a book is so that people don't have to remember it.
Finally, truth should be a property of beliefs. There should be no truth independent of beliefs, but the diagram shows that some truths are not beliefs.
So the world didn't exist before there were people around to know about it. Dinosaurs didn't exist.
The wikipedia diagram is wrong, but so are you. As others have commented it seems to represent the idea that knowledge is justified true belief. I have already explained that knowledge need not be belief.
As Popper pointed out in Chapter I of "Realism and the Aim of Science" justification is impossible, unnecessary and undesirable. If you assess ideas using argument then the arguments have premises and rules of inference and the result of the argument may not be true (or probably true) if the premises and rules of inference are false. You might try to solve this by coming up with a new argument that proves the premises and rules of inference but then you have the same problem with those premises and rules of inference.
It is perfectly possible for an idea to solve some problem and so to constitute knowledge without it being true, so knowledge need not be true either. Knowledge is not justified true belief.