In the book "Reinventing your life", it explains a bit about how this happens. Basically the kinds of situations we grow up with when we are little and our minds as well as our bodies are just growing and forming themselves, as adults we have a kind of natural chemistry to be in some way attracted to similar situations as adults. So for example if our carers were abusive to us as children, then as adults the kinds of partners who we feel attraction, excitement, chemistry, connection with tend to be people with similar abusive traits. People who are not abusive at all don't tend to get onto our radar or don't elicit any particular feelings in us, or we see them as a different kind of person not in the same league, or something like that.

I think it works the opposite way around as well - so someone with a kind of narcissistic or abusive personality will not feel happy and at ease with someone who has a robust self esteem and is showing it through all kinds of little ways, how they react to things, their body language, the kinds of thing they say and do etc. They will feel more comfortable and at ease with someone who seems anxious to please, who doesn't usually assert their own wishes or opinions, etc. So these things can be perpetuated on both sides without it necessarily being a conscious choice or decision.

Of course it's awful to be in abusive relationships and nobody would want that. It's just a mysterious and kind of unfair thing about how our minds work, that we tend to be attracted to the same thing we have lived with in the past even if that thing is awful.

I think Fuzzybear is right that healthy boundaries are key. The tricky thing is that it takes a certain amount of self esteem and belief that one is deserving of protection and respect in order to assert healthy boundaries. But then also in my experience asserting healthy boundaries is good and supportive for self esteem. So it can be a virtuous cycle too.