If engineers are not on board, how do you build rapport with them and influence them?

"I was interviewing for a CL6 PM role as a campus hire, so this may not map exactly to what lateral candidates get. After a basic recruiter screen, I had three rounds, and every single one was with product people. The first was with someone on the team, the second was with two PMs from a sister team, and the last was a short hiring manager conversation. What really stood out was how non-technical it was. There were zero case studies and the whole thing was behavioral."