At that scale, there will always be inefficiencies and imperfections. I also don't think a big mass firing was a smart move long term, but it does make some investors happy for some reason, and gives a short term stock boost.
In a bull market, large companies don’t want the negative publicity that comes from layoffs. So instead of firing them, they get shifted into underperforming teams.
The axeman cometh with the bear market. That unwillingness to tell people you’re cutting costs suddenly becomes exactly what they want to hear, so you take the opportunity to get rid of all those underperforming teams.
It’s garbage collection at an organisation level. This is capitalism.
I work at Google. I've seen this one time. A manager didn't want to do the hard work of firing somebody on their team and then misrepresented their productivity to another manager when that person tried to switch teams. This manager received a bad performance review and left the company (I don't know if it was their choice).
It is easy to move teams within Google (or, it used to be at least). But it is very hard to move teams within Google if you have bad performance reviews. You can't really shift underperformers to underperforming teams at scale.