WhatsApp has competitors that in Telegram/Signal etc. that are financially stable, offer more features and security, and with the mood of the government right now they would absolutely be prevented from purchasing. They would destroy WhatsApp in weeks if they did that.
Amazon is fine and doesn't need to grow. Facebook is in danger and growth was already priced in. Now it's not.
heck, soms European politicians are calling for a split of WhatsApp from Facebook because Facebook did not honor their end of the deal when they bought WhatsApp.
fb hilariously claims that this would be impossible, which is kind of proving they didn't hold up their end of the bargain.
Amazon is fine and doesn't need to grow. Facebook is in danger and growth was already priced in. Now it's not.