Why so quick? and am I that easy to be replaced? did I not impact him while we were together? I was so good to him?

We broke up 3 months ago and he went back with his ex again. I was such a good girlfriend I attended his football games. We broke up because he lied to me but pin it on me but he was in the wrong. Why did he get in a new relationship so quick? It hurts to think that I’m easy to be replaced which I know I’m not.
Why so quick? and am I that easy to be replaced? did I not impact him while we were together? I was so good to him?
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