Why did Justinian fail to reconquer the Western Empire?

Justinian's ambition to reconquer the Western Empire was profoundly undermined by the outbreak of a devastating plague, commonly referred to as the Plague of Justinian. This plague struck around 541 AD, significantly impacting the population of the Byzantine Empire and causing widespread mortality. The loss of a substantial portion of the populace weakened the Empire's military and economic resources, making it increasingly difficult for Justinian to maintain the necessary forces for a sustained military campaign in the West.

Moreover, the plague created social and economic turmoil, diverting funds and attention from military ventures toward dealing with the immediate crisis of illness and death. This catastrophic event compounded the challenges Justinian faced, as his resources were spread thin and not only affected troop levels but also weakened the morale and stability of the Empire during a critical period in his reign.

In contrast, while there may have been issues with military support, local resistance, or external distractions from other powers, the plague was a unique and widespread catastrophe that directly impeded Justinian's reconquest efforts, making it the most significant factor in his failure to achieve this goal.