Here's what he did say (his full post is here [1], if anyone's curious), which I think indicate culture, area, and distance from where he considers home as the factors affecting his health:
But what I've realized is that the last few years of living in such a singular environment have taken a huge toll on my life and started affecting my health. My friends, what I consider to be my home, and my life are back in Silicon Valley, which is also much closer to my family. Seeing how much I've left behind these past few years, it is clear to me that the time has come to return.
Specifics or misquotes aside, if you meant that the offer from Facebook was his primary reason for leaving, I can see that too, so won't disagree with the notion.
[1] https://www.facebook.com/hbarra76/posts/10154010035641612