Popular, oh, so popular
Popularity ... at a cost
Our current codebase has parts that are over 10 years old; and we hope our new codebase will last this long too. It seems that if we start writing Angular today; we'll be forced to rewrite the frontend in three to four years at latest (and with the way apps are going, the frontend is likely to be a large codebase). This doesn't sound very attractive.... We need frameworks that are stable and supported long-term; not that are constantly inventing new concepts and being rewritten with breaking changes every 5 minutes.
Ready for a different kind of enterprise computing
You have to look at what made (and keeps) Angular so much more popular than its competitors. The framework does not have strong opinions about conventions; this makes learning it much simpler. While some argue that this flexibility is a what makes it worse than opinionated frameworks such as Ember, that is only looking at the downside.
The ease of getting started enables more developers to learn it and its usage better adapts to other technologies you might use along side it. These reasons are hugely important to large organizations that need to hire and develop at scale. This is how Angular got to where it is, and will likely continue that momentum for the near term.