What is more important to be a product manager ?

It’s actually neither. But in the current job market, domain knowledge seems to be given a lot of priority

Its like asking and engineering manager what is more important domain or tech knowledge

Bias. Both are highly interdependent variables. You cannot develop one, without the presence of the other.

Technical knowledge is to ensure you can build products. This is like writing an app for a set of use cases. You can learn this with engineering , but it is pig Latin for people who are not from a STEM background. You can learn this with time.

Domain knowledge is to make sure you truly understand what it is to build products for a market. This is where time, intelligence, craft and taste of Product management come out. Users and their requirements shine and matter more than technical aspects.
This is not easy to learn, folks continually learn this as part of their day to day.