The reasons for the decisions are different each time. As for Android, we felt that IntelliJ IDEA Community Edition didn't have as much uptake was we had expect

The reasons for the decisions are different each time. As for Android, we felt that IntelliJ IDEA Community Edition didn't have as much uptake was we had expected, and we thought that adding Android support to CE would be a great way to make it more attractive without endangering the revenue that we get from selling IntelliJ IDEA Ultimate to enterprise customers. Of course, with the Google partnership that came later, the decision turned out far better that we had originally expected. :)