Unfortunately the smaller companies don't have a choice. Many acquisitions from Big Tech come with a threat - sell your company or we will move into your space and tank your valuation.
Sometimes they simply don't have a viable path to staying independent and profitable. Discord has tried a few things to earn more money (premium subscriptions, a game store) that didn't work out. I don't think they have a lot of options other than selling.
Did they not work out? I see people boosting servers and people with paid accounts very often. It seems they had a market willing to pay.
They make revenue, but I don't think they profit. I honestly doubt my $5 subscription offsets my costs as a user + my share of the unpaying users. Not that I pay that close of attention to their financials.
I think compared to Microsoft's offer, no.
discord is too big to be killed this easily. any msft copycat will be like facebook trying to kill snapchat