How can a TPM be helpful if they are not the most technically advanced person on the team?

In a word, abstraction. A technical PM is usually NOT the most advanced technical person on a team. However, they are able to break through sufficient tech layers to be able to contextualize the tech in the overall product development. They are able to draw the bigger picture of how components fit together, what technology elements are critical. And how to think about investment in each technical area - sucvh as build/buy/partner. In this way, they're not competing with others on technical know-how, but using it as an essential area of overlap to allow easier communication and collaboration.   

A techical PM is simply able to engage in more meaningful planning, discussions and collaboration on technology areas with other counterparts. 

In my opinion, you can be successful in any role by not having the expertise if you recognize it and are willing to learn. The product manager is generally not the most technically advanced person on the team, but they bring in other expertise and experience to the team (e.g., customer data, market insights, etc).

What has helped me is identifying key experts in the organization and leaning into them. I've usually not found a single technically "advanced" person on any of my teams. Different members of the team might have expertise in different areas. PMs with the expertise to identify these members and leveraging their knowledge can be successful in any role.

Being the most technically advanced person on the team is not necessarily a prerequisite for a technical product manager to be helpful. While technical knowledge is certainly important, the role of a technical product manager involves more than just technical expertise. They are not expected to do everything a software engineer would do.

Here are some ways in which a technical product manager can be helpful even if they are not the most technically advanced person on the team:

1. Customer empathy: Technical product managers bring a deep understanding of their customer's needs and pain points. They conduct customer research and use this information to inform their product development decisions.
2. Strategic thinking: A technical product manager can help the team think strategically about the product and its goals. They can help prioritize features and ensure that the product aligns with the company's overall strategy. This involves understanding the market, the competition, and the needs of the users.
3. Product roadmap: A technical product manager can help create a product roadmap that aligns with the company's overall strategy. They can work with stakeholders to prioritize features and ensure that the product is delivered on time.
4. Clear communication: A technical product manager can bridge the communication gap between the technical team and non-technical stakeholders. They can help translate technical jargon into language that non-technical stakeholders can understand and vice versa. This can ensure that everyone is on the same page and can contribute to the project in a meaningful way.
5. User research: A technical product manager can help gather user feedback and conduct user research. They can work with the UX team to understand user needs and ensure that the product is designed with the user in mind.