I believe cheaters can change but I don't think they can change for a partner who stays with them after cheating. And even if they did the trust will never be full and whole anyway. You did the right thing. Hopefully they betters themselves as a consequence of your correct decision to leave them.

I'm sorry this happened to you, it might take a while to get over and have an impact in your future relationships and ability to trust. Keep an eye on that and if you are struggling with trust even when there is no reason to reach out to a therapist for help.