There’s less than 1% chance Facebook messenger would be able to live to the philosophy of “no ads, no gimmicks, secure messaging”
That’s why startups can disrupt. It really does reward bottom up innovation.
Facebook is a growth at any cost kind of company. They really wouldn’t have listened to him even if he joined Facebook in the first place.
The messenger on Android sends all your text messages and phone logs to Facebook. Mark approved that in the name of growth.
There’s absolute no way Whatsapp would have been invented at Facebook. Facebook only bought it because it could have been a serious threat to their dominance.
So there's no way they would have listened to Acton and let him build Messenger the way he wanted.
Add to that the fact that Acton's ideas didn't yet have any market validation. Once WhatsApp was a proven success, FB was willing to pay for it, but even so they are now destroying what made it good - https://www.theverge.com/2018/4/30/17304792/whatsapp-jan-kou...