Why did he still choose her? will he come back?

We have been best friends for two years, both in on and off toxic relationships that are almost identical neither of us getting the time or attention we desire, everywhere we go with our partner it’s arguing and miserable. We’ve had hidden feelings for each other for the entire time growing deeper with time. Finally, 2 years later we are both single, but I am a year out of my relationship and he is fresh out of his relationship we are so excited to get to start seeing each other we jump into everything a little too fast. It’s magical, we both say we’re perfect for each other and that it’s meant to be. Reality sets in that we’re moving too fast bc problems arise. Basically he walked all over his ex bc she had no boundaries, but she also wasn’t loving or nurturing towards him. It’s like he wanted what I had to offer but also to still be able to have zero boundaries. We take a pause and a few days later his ex comes back around saying she misses him he starts to get confused. He tried to have us both but was lying to both of us about each other so I decide to tell her and she goes off on him. She told him to block me if he wants her in his life and he did. He knows they’re no good for each other but he’s also pissed at me for telling her. Why would he choose their relationship over ours?
Why did he still choose her? will he come back?
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