The question is perhaps what the shape and status of their tech stack is. Obviously, they are running at massive scale, and they have grown extremely aggressively over the years. What's more, especially over the last few years, they have been adding new product after new product. How much tech debt have they accumulated with that "move fast" approach that is now starting to rear its head?

I think this is probably a bigger root cause and is going to show up in different ways in future. The mere act of adding new products to an existing architecture/system is bound to create knowledge silos around operations and tech debt. There is a good reason why big companies keep smart people on their payroll to just change couple of lines after a week of debate.