Slack is a great story. Basically a tool they built in-house, the company were going bust and they realised that the "tool" had some value and out popped Slack https://review.firstround.com/From-0-to-1B-Slacks-Founder-Sh...
In fact the gaming company had already failed. They shut down the product and laid off employees, and offered to return the remaining money to their investors. The investors instead said keep it and try building something else. It wasn't a random pivot either. Real-time multiplayer gaming and real-time group chat share a lot of the same characteristics. Discord has the exact same origin story.
i mean... yes we have n=2 data but does that claim pass the sniff test? group chat is a lot easier graphics and physics and latency wise