@arthur-dent got it. I would hope that if it’s that many let go they find that thousands were necessary and hire them back. Otherwise that’s some serious bloat
I'm not in Musk's head, but it sure seems like they went into this thing with the pre-ordained conclusion that they were going to fire as many people as possible, and then they simply did that, without any consideration for how necessary operations might continue. If I'm reading that right, it's perfectly natural that they will find quite a lot of them were necessary.
In business, you often find companies expanding and contracting workforces based on business cycles. Business growing? Hire more people to keep up with demand. Business stagnating? Cut people to reduce costs. But those business cycles don't really exist with government services. To point to the example in the OP, it's not like the services provided by GSA were suddenly not in demand. Government offices don't suffer through or react to business cycles like private enterprise does. They still need to be staffed, office space still needs to be managed. Etc.
Again, I could have Musk entirely wrong on this, but my impression was that he was cutting for the sake of cutting, and now we are seeing the inevitable bounceback from them not doing enough thinking and planning before making the cuts.
This is exactly why the "We need to run the government like a business" crowd are morons.