In 2009, Brian Acton and Jan Koum originally founded WhatsApp “as an alternative to pricey SMS services”. SMS stands for short message service, better known as text messages. After Facebook purchased WhatsApp, Koum joined Facebook’s Board of Directors.
Acton resigned from Facebook in September 2017 and Koum announced his decision to leave in May 2018 shortly after the data leaks scandal at Cambridge Analytica. Both men basically left because they disagreed with Mark Zuckerberg (Facebook CEO) and Sheryl Sandberg (COO) over how Facebook wanted to manage data privacy and allow advertising on WhatsApp.