Products that get mission-believers first can get stuck on a small hill.

People who believe the mission might be willing to use a product that isn't great… but no one else will be willing to.

The product should be good enough that even people who don't believe in the mission will use it.

The mission should be a bonus, not the main thing.

That implies the marketing should be aimed at non-missionaries; the missionaries will be willing to do a bit more work to connect the dots.