There needs to be some evidence that what you are asking to build is worth building.
Deep Knowledge of the Customer
A PM needs to be an acknowledged expert on the customer: their needs, pains, desires, how they think - and for business products, how they work, and how they decide to buy.
This informs decisions that need to be made.
Need qualitative learning (the WHY), and quantitative (WHAT they are doing).
Deep Knowledge of the Data
PMs today are expected to be comfortable with data and analytics
A big part of knowing your customer is understanding what they are doing
PMs will usually start their day with 30 minutes of analytics
They usually look at:
Sales analytics
Usage analytics
A/B tests
Deep Knowledge of Your Business
A deep understanding of your business, how it works, and your role is critical for PMs
You need to learn who your stakeholders are and the constraints they operate under