when let's say when Hudson found the Hudson Bay why didn't he claim all of ruperts land when he got there or all of Canada or North America wouldn't it be more useful if you just claimed all the land in the world there's no contention for land and your nation becomes the largest nation in the world is it rules of colonizism because they didn't really colonize when they found the new world and still owning all the land in the world or keeping some rules
This is a question that relates to the development of public international law. When the european exploration started in earnest, Spain and Portugal (the first europeans to do so) divided the world between them. They signed - with papal support - the Treaty of Tordesillas.
This was later contested by other european powers. They claimed that in order to truly be able to claim land, you have to exercise actual control. This principle was based on roman law and is called "uti possidetis".
Therefore, just discovering land would not grant a permanent claim to it. Other powers would not have recognized a claim without actual control, as the Treaty of Tordesillas was not recognized except by the original signatories.