You’re saying slack beat lync/communicator, forcing microsoft to build a competing product from scratch…because their enterprise sales was better?
Also before Slack the competition was less Lync or such, but Mail, jabber and non-sanctioned chat (Whatsapp etc.)
The silliest part is you actually have the cause and effect exactly backwards in two different ways (nobody cares about integrations if they don’t want to use your product in the first place, and slack’s early momentum was specifically due to being freemium + product-led rather than enterprise sales)