Stephen Hawking cheated on his wife with a nurse after his wife had supported and cared for him for 30 years. The nurse was also the wife of the man who created his speaking device.
That guy was never a good person.
Unhealed trauma makes you tolerate so much shit you don't deserve because you don't want to lose people. Healing teaches you; losing them is better than losing yourself. You realise some people don't deserve access to you — no matter how much you love them.