And in my experience the opposite applies as well. Having a PhD in a field providing the necessary background in theory doesn't necessarily imply the skills and experience required to produce useful models.
In your experience, what personal characteristics, educational background or personal trait did successful individuals have?
That's a really good question. The best people I've seen so far have had a willingness to rigorously align their models with reality, plus the knowledge and/or experience to know what to check. Verifying assumptions, picking evaluation metrics appropriate for the problem, checking for model interpretability, checking that model decisions are sane, and so on.