It's hard because toxic people (narcissistic) simply don't care unless there is something in it for them. They can be very nice too, they have learned how to be charming and manipulative. So, often you don't really notice the red flags right away.

That man Bernie Madoff, he manipulated a lot of "smart" and successful people out of their money, people were so ashamed when they found out he spent their money, people like Stephen Speilburg who are very intelligent and successful.