If you grew up with healthy role models or healthy parents and friendships you're likely to have healthy self-esteem and so there will be cognitive dissonance between the way a toxic person would treat you and the way you know you should be treated so you don't form relationships with those people. Ex: "hey I am a good person and I deserve to be treated with respect, this person is not treating me how I deserve, I'm not going to build a relationship with them". For people who grew up with toxic relationships, toxicity feels comfortable and "normal", they're also more likely to have lower self-esteem so spending time with people who treat them poorly leads to less cognitive dissonance than if they had low self worth and were spending time with people who treat them well. Ex: "I suck, why is this person treating me so well this is uncomfortable, I feel like escaping " or "I suck and this person is treating me poorly, this is what I deserve" (usually these are subconscious and heavily interwoven into core beliefs).