Most of your post addresses the fact that these firings had NOTHING to do with efficiency. Which is 100% accurate. I don’t believe there has ever been an attempt to identify the savings resulting from these firings - other than simply reduced workforce. But no assessment at all as to the quality of services provided.
A slightly different issue is the manner in which these were done. A month or 2 ago, when these were happening, I was pretty up on the intricacies of what was going on. But since my job was not ended, so much other crap has gone on that I forget the specifics.
With most of the folk who were fired, they included language about poor performance. The only explanation for that was intentional cruelty. Many of those folk had recently received glowing reviews and/or promotions.
Some people were in their probationary periods - usually 2 years, sometimes 1. Those folk can be fired at will. Many of those folk were fired - despite the fact that they performed vital duties. Some of them were rehired. The clear intention was simply to fire ANYONE who could be fired - with ZERO assessment of whether doing so would increase efficiency (or not cause harm.)
There was another group of folk who were probationary as a result of recent promotions. Folk who had worked for a number of years, done well and gotten promoted. But in their new position they are probationary for 1-2 years. I think there was an issue with the apparent inconsistency between favorable reviews and poor performance language.
Then there were folk who were not probationary, who were fired seemingly inconsistent with their collective bargaining agreements. A lot of stuff was done which seemed blatantly inconsistent with CBAs. My impression (which I believe is correct) is that the admin was happy to simply fire whomever/do whatever they wanted, and force the individuals harmed to challenge the actions. Assuming that as time passed, many people would get other jobs, whatever. The initial court challenge by the unions went nowhere, as the courts (IIRC) held that the sole recourse was through the Merit Systems Protection Board (MSPB). At the time, the MSPB did not even have a quorum, had a huge backlog, and is notoriously slow. Not sure if they have a quorum now.
I just offer this to suggest that the issue of federal firings is somewhat complex, involving differently situated groups.
Who are these agency heads, and who appointed them?