It is not about net neutrality, it is about them buying bandwidth as cheaply as possible. 54.8Tbps now split in some proportion amongst the investors, 2.5x that once they upgrade to 100Gbit optics.
Super high-speed connections between South East Asia, China, and Japan will benefit everybody. It will be the backbone of cheap hosting in the SEA region.
Sounds like "outside are of core competency" to me. What does anyone a Facebook know about undersea cables?
What does anyone at Facebook know about throughput? A lot(1).
This has nothing to do with net neutrality. Pretty much every big company in the world has their own backhaul connections between their data centers; not everything goes over the public Internet and not every piece of electrical wire or fiber optic cable is for the public Internet. In fact, the Internet itself is just a bunch of private networks that have agreed to exchange traffic.
Do you think Facebook is investing in infrastructure to reduce their own network costs (by traffic swaps)?
There are many reasons for this, not just cost, but also link quality, latency, non-contention etc...