Why is he ignoring me after breakup?

Perhaps he needs time to heal after the breakup. Maybe he needs to realize what has happened between the two of you and learn how to heal himself. Talking to you after the breakup may manifest feelings within him that would make it harder for him to move on. He may also need time to collect his thoughts so he can speak with you in a way that does not hurt the both of you and leads to an effective conversation. He may also believe that the time apart may benefit you in your healing process. He may be reflecting on how to better himself for his own purposes or for you.

He could be ignoring you after a breakup as a way of coping with the loss of the relationship. He might not want to feel sad and by doing that he thinks ignoring you is the best option. In my personal experience, an ex-boyfriend stopped answering my texts, calls, anything of us on social media, etc.. He later on said he did that because he couldn't handle the loss of the relationship and did everything he could to not think about me. Some people deal with situations by avoiding their feelings and/or cutting ties quickly. A breakup is incredibly challenging, but it gives you more time to think about your worth and focus on what you want to do.

There can be several reasons why an ex ignores you after your breakup. He might feel abandoned, lonely or maybe even relieved. If the breakup was something that he didn't expect, he would need time to clear up his mind and forget about you considering that he might still like you. He will obviously avoid interacting with you if he still likes you and therefore the person that get hurts is himself. He might need to get you out of his head which requires time in order to forget you. On the other hand, if the breakup was something he had anticipated, he might feel like your two's relationship is completely over now and might want to find new people to talk to.