It does makes sense; Salesforce has been trying to be the operating system for work and real time communication was lacking. When I was there, we used Chatter

It does makes sense; Salesforce has been trying to be the operating system for work and real time communication was lacking. When I was there, we used Chatter in org62 and it was awful. Yet a lot of time and money was invested into trying to make it work. With Slack, they have a very easy upsell for their enterprise customers to keep them away from Teams; as well as inheriting a huge userbase that is very familiar with Slack – imagine getting feeds from Marketing and Sales Cloud on a slack channel, taking customer requests directly on Slack via Service Cloud, etc Note that these are mostly things you can do today, but by bundling it into the Salesforce suite of products they will greatly increase adoption by cross-selling.