will probably get into reasons for breakup in the next couple chapters. but basically its based on Wanda using her mind control on him despite having promised to never do this.
and wanda thinks he abandoned her because of this, when he doesn't free her from prison.
Dude wanda doesn't deserve Wei after what she did.Wei practically sold the rest of his life to see wanda and when he does she breaks up with him and goes with someone else.