I have some data here. For years, I used "candidate fit tests" (offered by Pittari.io). It's like Myers-Briggs but focused on workplace style & drivers. For successful PMMs, I noticed a pattern. When it comes to workplace style, PMMs scored highly for "commanding" and "outgoing", favoring an "easygoing" style more than "exactlng". In other words, they like to enage with people and push conversations forward, but they're still flexible in groups. Then, across 7 possible drivers, PMMs scored highest on creativity and altruism. This makes a lot of sense for positioning work, and "atruism" echoes Jenna Crane's answer about empathy. The PMMs were less motivated by "individualism" (i.e. they're generally not mavericks).
Though I like using the Pittari test to spark a conversation, I'm sure you can assess these traits through behavioral interviewing.
Sidenote: If you look for these traits, you can find hidden gems in unlikely places. One of our best PMMs at Twilio came from a completely different role in Marketing Ops with no PMM experience. If the hiring manager only looked at resumes, it wouldn't have happened.