I don't think this has anything to do with "Skype for business"? At least from my perception what happened was that a program+app that once simply just allowed

I don't think this has anything to do with "Skype for business"? At least from my perception what happened was that a program+app that once simply just allowed two persons to talk or videochat between phones and/or PCs, became more bloated, buggier and more demanding, forcing people to look for a simpler better working alternative. This alternative seems currently whatsapp. Til that one becomes too bloated and buggy I guess. Then there'll be a next one.