[skybrian]

As I understand it they also had a stronger focus on usability for first-time Internet users in many countries. For example, porting the app to many devices (not just smart phones) and using phone numbers as user identifiers instead of usernames.

I don't know if you call that tactics or strategy, but it made a difference for user growth. Users don't care who invented it, they care if they can get it to work easily.