Prophecies regarding the end of days carry a natural tension between the human desire to decode the future and the divine will to keep it hidden. Daniel, having received a vision about the final days, is instructed to conceal its true meaning from future generations until the proper time arrives. This instruction acts as an urgent warning [מצודת דוד]. Even if Daniel understands the exact details of what is to come, he must write his prophecy using hints, intentionally leaving the message blurred without adding further explanation [אבן עזרא, יוסף אבן יחיא, ביאור שטיינזלץ].
There are different reasons for this secrecy. It may serve to keep hidden truths away from those who are unworthy of them [אבן עזרא]. Alternatively, since the time of redemption is set in the distant future, revealing the exact date would cause people to lose hope. Keeping the timeline a secret allows every generation to hold onto the belief that redemption will happen in their own lifetime [מלבי״ם].
Despite the message being sealed, people will never stop searching for answers. This search involves moving back and forth in pursuit of God's word [אבן עזרא, ביאור שטיינזלץ]. On a deeper level, this describes a movement of the mind. People will constantly investigate, study, and use their intellect in an attempt to figure out exactly when the redemption will occur [מצודות].
Because of this intense study, knowledge will indeed increase, though there are different views on what this actually achieves. One perspective is that all historical attempts to calculate the end are doomed to fail. Every calculation will eventually be proven wrong because God intends for these mysteries to remain completely misunderstood until the right moment [מצודת דוד, יוסף אבן יחיא]. On the other hand, as time moves forward and the final redemption draws closer, the window of doubt naturally shrinks. Humanity's understanding becomes clearer simply because all the past, incorrect dates are ruled out [מלבי״ם].
The primary approach among commentators is that the mystery will only be solved when the final days actually arrive. At that point, the veil will be lifted from the book, the eyes of the wise will be opened, and the true meaning of the hints will be perfectly clear as God returns His people to Zion.