«لِقُوَّةِ الْأَسْبَابِ الْمُتَّخَذَةِ فِي حُصُولِهِ»
Because the means adopted for its realization are strong.
Example: «إِنِ اشْتَرَيْنَا كَانَ كَذَا» — If we make the purchase, such-and-such will happen. The purchase may remain future, yet the planned means are represented as robust enough to warrant decisive expression.
The value lies not in making a false claim about past time but in rhetorically presenting a future outcome as firmly anticipated. The underlying context still determines whether this is confidence, wishfulness or exaggeration.