While I don't agree that quality is in any way declining, I do understand the move is easier. Europeans are in love with Facebook, not Apple. Makes it easier to switch device platforms, for sure.
No, that's really not the case. Facebook's reputation is not good at all here (in Europe), whereas people are shilling for Apple all the time. It's just really nice to have a messenger that is not tied to a hardware platform, and WhatsApp became popular before it was bought by Facebook.