I think a significant part of the problem is that those of us with trauma tend to unconsciously navigate towards people who will replicate the patterns we have learnt with others. Obviously this is as true in relationships outside therapy as in it.

Both my first two ts were assigned to me as I didn't have a choice who I saw due to the circumstances in which I sought therapy. Both of them turned out to be exactly what I needed at the time so I was incredibly fortunate. Had I been left to choose a t, I'm not sure I'd have been capable of discerning a good one. I saw another t some years ago who I did choose but looking back she wasnt a good match. My current one is and I feel I'm in a place where I can know and seek out a respectable t.

It's a very difficult issue and the only way around it really is better training and regulation of therapists so that people can't go into the profession to exploit the vulnerable, consciously or otherwise.