TL;DR
US sanctions.
Longer Version
After Trump took office in 2016, he started pressuring US companies to cease relations with any Iranian entity. This resulted in all Iranian apps being expelled from the App Store in 2017. However, we didn’t sit ducks waiting for some miracle to happen. We started using Enterprise distribution to get our apps to our users. Even though we lost all the good things offered to developers in the App Store (discovery, automatic updates, etc.) this helped me learn a lot about app distribution mechanisms such as Development vs. Distribution Certificates, Provisioning Profiles and Code Signing. This led to the improvement of iOS App Signer as a helper tool to automate parts of our complicated release process.
Here’s a Harvard Business School Case Study about this: Snapp: Scaling Under Sanctions in Iran.