Why do some people who got cheated on in the past still cheat on their current partner?

Why people who said they’ve been hurting by their ex in the past by cheated on them, cheating on their current partner when the partner just trying to give the love they wanted. They know exactly what how it feels like.

I mean i’ve been there, my ex cheated on me. I know that feeling that’s why I won’t do it to others. My close friend cheated on his girlfriend while I know exactly how his reaction and how his feelings when his ex wife cheated on him just a week after they got married. I’m confused, now i started to think that maybe his ex wife cheated on him because he cheated first😂😂
Why do some people who got cheated on in the past still cheat on their current partner?
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