This quote means that when an enemy is close by and is not taking action, they are likely confident in the strength of their position and are relying on it to protect them. Sun Tzu is saying that in this situation, the enemy is not taking action because they believe they are in a strong position and do not need to take action to defend themselves.
When a competitor is nearby and remains inactive, they are likely relying on the inherent strength of their position in the market.
When a competitor is nearby and is not taking action, it is likely because they are confident in their own position and do not feel the need to compete or respond to your actions. This could be because they believe they have a strong market position, a loyal customer base, or a competitive advantage that allows them to remain confident and quiet.