The defeat of the Marathas in the third battle of Panipat can be attributed to several causes. The options provided in the question list out these causes, and we need to identify which of them led to the Marathas` defeat.

Option 1 mentions "tactical errors by Sadashiv Rao Bhao." This suggests that poor decisions or strategies taken by Bhao played a role in the Marathas` downfall.

Option 2 states the "superior generalship of Ahmad Shah Abdali." This implies that Abdali`s leadership prowess and tactical expertise contributed to the defeat of the Marathas.

Option 3 asserts the "presence of a large number of non-combatants in the Maratha army." It suggests that the inclusion of non-combatants, such as civilians or non-fighting personnel, in the Maratha army negatively impacted their overall combat capabilities.

Option 4 highlights the "treachery of a commander, Ibrahim Khan Gardi, of the Maratha army." This indicates that the betrayal by Gardi, who may have sided with the opposing forces, influenced the outcome of the battle.

After evaluating all the options, the correct answer is option 1. This means that the defeat of the Marathas in the third battle