Why do people think Thomas Cook discovered Australia when it was really the Aborigines?

No man named "Thomas Cook" is credited with discovering Australia.

James Cook is the man wrongly credited with discovering Australia.

Aborigines had inhabited the continent for thousands of years, and Macassan traders from Asia had been visiting for years to collect sea-slugs, a valued delicacy in Asia, long before the first European sighted the continent. The first recorded European visitor was Dutch explorer Willem Jansz/ Janszoon, who landed on the shores of Cape York Peninsula in 1606.

James Cook was the first to chart the eastern coast, and the first to send back a favourable report on the continent, where previous European explorers had disregarded it as of no value. Because Cook recommended "New South Wales" for settlement, and his views were strongly endorsed by scientist Sir Joseph Banks, Australia came to be considered as a site for a new penal settlement for Britain's convicts. Australia was colonised by the British, and thus the British viewpoint prevailed, dictating that James Cook had discovered the continent which had been known by Europeans for at least 150 years.