> happen to be always wrong

Which is very very unlikely. When you don't know the answer, you'll guess, which is like flipping a coin.

Suppose you have zero knowledge and always guess the answer. Can you get unlucky that you get more wrong answers than correct answers? Sure. But the more questions you get, the closer your accuracy is to 50%.

Another way to look at it is to realize that a binary prediction has the highest entropy (uncertainty) when it splits fifty-fifty.