Slack just learned what it means fighting against the big four.
After spending money on a full pager in the NYT (November 2016), claiming that slack is just the superior product and that they understand customers much better.
Reality strikes, as on September 2019 MS Teams overtook slack in regard to daily active users.
Now they face the problem of fighting a war that seemingly can't be won.
Especially because COVID-19 has accelerated the adoption of teams much more than it has for slack.
As a publicly traded company, slack has now to also protect it's business, so it's fair to cry foul towards the EU, if this will in the end lead to the outcome slack hopes is debatable.
The more relevant question for slack going forward will be to answer what they will do strategically and what they want to establish as their USP.
Ben Thompson did a great job looking into the dynamics between slack and MS Teams here:
The oversimplification of Ben’s point is this:
Positioning slack as a new form of social network, which would allow slack to offer something which seemingly Microsoft doesn’t have right now. Since Microsoft is aimed towards creating the all-in-one solution internally for companies, but not so much for collaboration between different firms.