Main reason for Kotlin uptake is Android. Kotlin is successful due to smaller footprint of its runtime lib and just-slightly-better Java philosophy, because it

Main reason for Kotlin uptake is Android. Kotlin is successful due to smaller footprint of its runtime lib and just-slightly-better Java philosophy, because it uses Java collections instead of bringing its own like Scala did. A big runtime library and problems caused by high method count hitting limits of Android runtime slowed down adoption of Scala on Android and allowed Kotlin to take that niche. Later the official support from Google reinforced its position.