Biden was backed into that corner - it's not like he is anti-union but of course having the economy tank from a union strike would have been catastrophic for his agenda and the economy (and Democrats staying in power).
In the case of Biden, his badness ("bad" because I'm pro-worker safety/rights) is less than Trump's because he wanted to defend the union but didn't want to make the economy suffer in order to do it and he didn't have enough political power to do more without losing other things vs Trump who went as hard anti-union as he could get away with.