No, it wasn't conscious, they just incrementally and iteratively optimized the site to maximize page views and ad revenue. Turns out that ends up eventually killing it - without ever having the intention of doing so. But you can rest assured that every decision on that long, slippery slope optimized some metric toward a local maxima.
It's been 8 years since my last post on Facebook and I visit less than 10 mins a year (only because I have one friend who uses FB messenger to communicate with me when he's traveling).