preparations to take such a long journey and survive. They'd need food, fresh water, a boat large enough to stay upright in the waves, adequate clothing, and so on.

To choose to make a long journey without knowing what lay beyond view would likely be out of necessity or adventurers who wanted to see what was out there. Either way, significant numbers had to make the trip to survive and to populate Australia.

Remember, European adventurers thought they were going to the "Orient" by sea, not that they were going to an unknown continent. People did not know that the earth was round and they wouldn't fall off the edge so they'd naturally be careful about long trips to places they'd never seen and didnt know existed.