1) Maybe brought on themselves: 'hey, design/build the thing, then fire those who designed it' type thing, which definitely happens. It happens to companies in a crunch, or those who just put the outcome ahead of everything else.
2) A decimation: let's use this as an opportunity to drop anyone we feel is not cutting it - and teams that we created/hired we realize we don't want/need.
3) General organizational shakeup.
4) A true and real opex cutback ahead of anticipated future needs.
The thing is - outside of human terms - it's a big cut but it might be highly rational.
'Pruning' I think is a essential aspect of any healthy organization, forcing entities to rethink, to shake them out of their settled positions, getting rid of organizational cruft.
Of course, there are humans behind every decision which makes it quite fundamentally something else.
But if you could imagine they were 'robots', as if to remove any issues of compassion and concern for externalized outcomes, and this were simply a simple dispassionate re-org ... then you can see where the economics might be pointing.
We also don't know the terms of the layoff: maybe some of them are voluntary. Maybe the payouts are huge. Sometimes these things work out well for a lot of those involved, obviously it doesn't for others.