It's a pretty big market. Apps like whisper are terrible and unmaintained but have 10M+ downloads. I would wager that it's apps like these that the average person uses, not the polished ones you see on Product Hunt.

From within the app, looks like most users are South American. Large population, and there's a shortage of apps targeting the region.

This is just my perception, being someone builds for the Indonesian market, and having an app that hit similar numbers without any marketing effort.