[jdeibele]

Facebook would like to see money from WhatsApp but it was far more important to them to block off a potential competitor.

WhatsApp could have provided services like Facebook or Instagram but cost a small amount of money each year. Maybe it would be per-user or maybe it would be a sponsorship, like what Discord is doing. Sponsor the local neighborhood group for $25/year, your high school class forum for $100/year (so you can show everybody "you made it big").

The key to doing something like that is network effects, which WhatsApp had in spades.

Probably it's inevitable that they would have descended into advertising and tailoring the site for advertisers instead of users.