The past cannot be directly perceived now. Information about it is carried by transmission and, where available, surviving traces. Tawātur is relevant because an event may be securely known through widespread and properly supported testimony.
For instance, the existence of a former ruler can be established through a convergence of historical transmission and other evidence. That does not guarantee every saying later attributed to that ruler.
The occurrence of an event and every proposed detail about it are distinct propositions. Certainty about one does not transfer automatically to the other. Students must identify exactly what a report has established rather than treating a broad historical narrative as uniformly verified.