In this case, MS Teams is obsessed with Office integration as it's key selling point. Which in turn means business workers. Whereas Discord users don't care about calendar integration and so on.
Modern chat apps are a Venn diagram with a modest intersection.
I can't see how Discord can get more users without losing original users. Basically, a demographic shift. And then you're in the big guys territory where they additionally have 'killer features' already and that's where businesses get bought or fold.