They recently switched from composite hull to metal hill for BFR/Starship, so it might be a case of terminating those employees whose primary focus was designing the composite hull and whose skills were not transferable. There will likely be talent pools that get thinned out too, welders who won’t be so necessary now that Block 5 is in production and Falcon Heavy is “operational” (meaning fewer expendable launches, less demand for welders to build new rockets).

It doesn’t help that there’s been little warning (though I guessing a lot of these employees had some warning that they are going ormtheir teams are getting thinned).

I hope for the best, the people leaving SpaceX have certainly got great resumes to recommend them to new employers!