To spite you it is a way of being passive agressive. He is trying to hurt you.
Because he is an ex that is moving on from u. And u should do that too... He is ur ex not ur boyfriend
Have an opinion?
He is moving on.
Because you may have hurt them or they may still like you and are trying to find ways to get over you.
They want you to feel the sense of exclusion they feel from you when you moved on with your life and forgot them.