Antonyms for the phrase "became a fact" could include "remained uncertain," "disproved," "discredited," or "debunked." These antonyms suggest that the initial idea or claim did not come to fruition or was proven to be false. Other antonyms could include "never occurred," "proved untrue," or "was refuted," indicating that the concept was never valid to begin with. In contrast to "became a fact," these antonyms suggest that the idea or notion failed to come to fruition or was incorrect, emphasizing the importance of critical thinking and fact-checking in today's society.