«لَوْلَا عَلِيٌّ لَهَلَكَ عُمَرُ»
Were it not for Ali, Umar would have perished.
This is an example of lawla, not bare law. It presents a factor whose presence prevents the stipulated outcome. The shared opening letters do not make the grammatical and rhetorical functions of the two particles identical.
The relevant task here is analysis of the condition, preventing factor and consequence, not independent verification of a historical attribution. The wording presents Ali’s presence as the factor preventing the hypothetical loss.