Some Cheaters are in loved with being loved.
The value that they placed on their relationship with you was in how you adored and pursued them. As soon as that slipped, they started thinking about finding another supply of adoration.
In other words, it was always about themselves. They never really loved you for you.
Until they deal with this reality, I think all their future relationships are ultimately doomed. Eventually, they shine will come off, and they will repeat the discard process. Cheaters are that shallow!
I find it oddly comforting to consider this dynamic. It makes the discard hurt less seeing that one’s Cheater probably was never real in the relationship for the right reasons–i.e. for you. I hope you find it comforting as well.