1. Emotional shock and time required to deal with: The other party may feel shocked, sad, or confused by the news of the breakup, and need time to digest this significant emotional change, so they are temporarily unable to respond.
2. Avoiding conflict or escaping reality: Some people may choose not to reply as a way to avoid direct conflict or avoid facing the pain of reality. They may not be ready to face the fact of a breakup, or they may be afraid that responding will exacerbate emotional fluctuations.
3. Not sure how to respond: The other party may be surprised by your decision to break up and is considering how to respond in order to both express their feelings and respect your decision. This uncertainty may lead them to temporarily remain silent in search of the most appropriate response.