So it makes sense to me that Google, which derives most of its revenue from search, would find the advent of LLMs to be existential to its core business. 

But why do you think Meta is investing as much in AI, given that social networks are pretty sticky and wouldn't necessarily be impacted from a business model standpoint?

Given the general negative reaction of Facebook audiences to AI, it's a very, very puzzling business decisions.  Seems more like a personal interest of Zuckerberg's than a rational direction for the platform to take.