What benefits did the Dutch want from secret possession of the new mainland?

As you know, for the first time Australia was discovered at the beginning of the 17th century (1606) by Dutch sailors. They kept the secret of discovering the new mainland for more than a century, despite the fact that the Spaniards also reached some Australian islands in the middle of the century. The purpose of this secrecy was to avoid a military conflict with more powerful countries and use the resources of Australia as a colony only for their own purposes. However, in 1769 James Cook declared Australia a British colony.