After a launch, there's lots to do. We still consider the project as an experiment, so we focus on "the product" or "the business" only to find it fizzles out. The whole project gets dismissed with "they didn't really care" but the real problem is their email is still sat in your inbox unanswered, or the price was too high, or it was too slow to really use.
Sometimes the idea is fine. It's just that you failed to hit some other baseline. If you're going to test customer interest, you have to really care about what they want to and , and you have to know their standards.
So first - learn what's important to them, establish acceptable ranges from prior behaviour, and design your experiment with those in mind.