While the hackathon easily allowed for supervised metrics, the real metrics come after the hackathon is over.
How useful is the product for the long-term? While some software is completely unique, with no other options on the market, most applications have alternatives. Once the hackathon is over, the product development team needs to track usage. Did the participants continue to use the product once the hackathon is over? Is it delivering results for them? Or did they use it for the hackathon and never log in again?
Each member of the development team is working on a specific task, in a silo, during the product development process. With the hackathon, they get the opportunity to see what their peers have accomplished and get introduced to the big picture, the full end result of their work.
While the hackathons help drive success for individual products, having hackathons as a regular part of the product stress testing reinforces the big picture to the entire team.