Surprisingly, this VICE article actually provides a better summary of the history between the two:
https://motherboard.vice.com/en_us/article/evqxgz/a-brief-hi...I can't shake the feeling that the launch failure cannot have been the initial cause for this fallout. Rockets sometimes fail, and I doubt that anybody believes the launch was intentionally sabotaged.
If I had to guess, Zuckerberg is envious of Musk's charisma and popularity. It can't help that Zuckerberg is a one-hit wonder while Musk has four or five successes that each, individually, could put you in the history books. Plus, obviously, every one of Musk's ventures except PayPal is cooler and more beneficial for humanity than Facebook.
Musk seems to be very good at picking up on these insecurities, and to push exactly where it hurts. Witness his comment on their AI disagreement, and how artistically it combines feigned boredom and arrogant dismissal: "His understanding of the subject is limited."
