Apparently, Disneyland and Disney California Adventure work under separate union contracts, and so, any cast member that had been working at California Adventure, and transferred to Disneyland to work at Star Wars: Galaxy’s Edge, lost whatever seniority they had.
And since seniority usually factors into any layoff, it meant that Galaxy’s Edge was hit hard as that’s where most of the “newest” employees could be found.
The reason Galaxy’s Edge has been the focal point of the layoffs apparently has to do with seniority, which is something that cast members working the new land largely don’t have.