Why was the death of darius impotent to alexanders conquest of Persia?

The death of Darius III was pivotal for Alexander's conquest of Persia as it effectively removed the central figure of Persian resistance, destabilizing the Persian Empire and undermining its leadership. Darius's assassination by his own men highlighted the disarray within the Persian ranks, which allowed Alexander to exploit the resulting power vacuum. Without a unifying leader, the Persian forces struggled to mount a cohesive defense against Alexander's well-coordinated military strategies. Consequently, Darius's death accelerated the collapse of Persian authority and facilitated Alexander's swift victories across the region.