Why did my ex go back to her ex-fiancé?

Me and LTR recently broke up. I’m 26 and she’s 29. Was with her for two years, didn’t work out.. now she’s back with her ex before me (fiancé age 36).

She was with her fiancé for 7 years, she cheated on him 3 times and even had an affair.. then she met me and broke up with him to be with me. I know I ignored the red flags btw but my post isn’t about where I went wrong with her.. I’m asking why did she go back to him?

After me and her broke up, we met again a month later and fucked in a hotel room. Then she told me she’s back with her ex fiancé. She told me my body is better than his, she still thinks about me and she has so much passion with me but he is her partner and she loves him.

I realised I could never see her again at that point because the damage had already been done. But I just can’t get it off my mind. I don’t understand why she has gone back to him.

I mean.. she cheated on him, had an affair and left him for me.. for two years.. and now they are back together and she’s happy. How is that so? He’s also bought her gifts and taken her on vacation. Why would he do that? He’s only validated and rewarded her shitty behavior. I would never allow that shit!

She said things to me like “he is so gentle but you are not like that.. that’s why we can’t be together”. I tried to tell her that being gentle doesn’t fucking matter because she cheated on him before and left him. If being gentle was all that she wanted then why would she do that?

My mind is honestly blown because none of it makes sense. I’m 6ft2 lean and make decent money, but not as much as him because he’s got 10 years on me. But honestly he’s a skinny nerdy looking dude.. doesn’t lift. She also told me sex with him is nothing special and they only do it once a week, but with me there is so much passion and we used to do it a lot. Her words.

So if this is how she feels... why has she gone back to him? Usually you hear of women choosing chad over beta but in this scenario she’s chosen beta. She said she doesn’t feel stable with me. She would also be jealous a lot. But she was mad attracted to me I know that. I’m not saying I’m an alpha god but I’m definitely chad for her and certainly compared to be fiancé. Yet she has chosen him.

Why is this happening? Both her and him are deluded.. she cheated, had an affair, left him and she says she loves him? He has taken her back after 2 years and knowing all of that, bought her gifts, taken her on vacation and she’s moved in with him. She told me “he was waiting for me”... ah yea so he’s like “my girl cheated and left me, no worries I’ll take her back and give her everything”

I would never do this. I was always strong with her and yet I’ve lost and the beta has won. Isn’t this backwards to TRP? Again I’m not saying I played the LTR perfectly and I fucked up in some ways but he clearly fucked up worse than me because she cheated on him and left him already. If she chose a new alpha or someone with their shit together, perhaps I could understand more... but him... she already doesn’t value him.

Can someone help explain this?