I'm sure FB improved its monetization and will continue to improve it as it grows as a company. But they also benefit from an overall increase on online ad spending - which is expected to grow 19% this year ).

https://techcrunch.com/2019/02/20/emarketer-digital-ad-forec...

Nearly 19% increase in online ad spending overall + FB's 8% growth + improved monetization and you can see why FB ad rev increased 30%. Online ad spending is expect increase by double digits for many years so FB, GOOG, etc are sitting pretty as long as they can hold onto and grow their userbase.

Even if FB did nothing, their ad revenue would most likely increase by double digits every year simply because the digital ad space is increasing by double digits every year. Money is pouring into digital space and they have one of the biggest buckets.