Full disclosure - I worked for MapBox for about 18 months and left as it was a miserable and fucked up place to be because of the internal politics and lack of competence in the geo domain.
The Washington DC team are a bunch of social warriors who spend more time preaching politics and activism versus doing their jobs. During the 2020 election campaigns several of the more conservative staff were actively retaliated on - code review comments like "This is the sort of code a Trumper would write..."
The SF team is a bit better as further from ground-zero, but not much.
The Belarus people get shit done without drama or complaints. They are the top performers in the company. They also avoid all the politics.
The union is nothing more than an attempt to stall the offshoring of all dev to Belarus and other locations due to the performance of the DC/SF teams. We have the social warriors protecting their nice do-nothing but get paid well jobs.
The company is on a path to a SPAC with Softbank so this was well planned timing to prevent that, or force some nice severance plans to allow the company to move forward.