The article doesn't actually say that the union is responsible for employees getting severance packages. The closest thing to a direct effect of the union is that some union members were offered a buy-out package to quit.
IIRC, four months pay and health insurance for those making > $110k and six months for everyone else...or something like that. That does seem pretty generous, especially for a company that small.
[0] https://www.theverge.com/2020/5/13/21257585/kickstarter-layo...