In an interview with IGN, Sony's Scott Rohde explained why so many people lost their jobs at Santa Monica, saying:
We’re always evaluating the business, and we’re always thinking about what’s going to be the best thing. But I think you know that PlayStation and Worldwide Studios has a pretty unique structure that really encourages creativity and exploration. And, of course, within that framework, not every title can be a success.
There’s not a single business on the planet where every single project that is started is a success. And that’s just what happened here. So sometimes, high profile projects or studios need a reboot, and that’s what’s happening here. Santa Monica will always be a hugely important part of our global family of studios. It’s still a huge studio that’s right up there around 200 people, even after the recent layoffs.
Last year's entry in the God of War franchise didn't sell particularly well for the studio. There's a good chance Ascension's underwhelming sales were a major factor in Sony's decision to mix things up.