The ruling is specifically about the facial recognition part of FB. They could end up paying $5 billion just because of facial recognition stuff .
Imagine if you put the Konami Code on the Google homepage, and got sued and lost for it. Then got fined $1 billion for it. You'd feel like you made a pretty bad decision there.
Obviously facial recognition is closer to the core of what FB is doing in general but it's still a lot of money for an incidental part of their system! They can pay it, but that's $5 billion they can no longer use to buy like... 10 startups or whatever.
I robbed this house, but it was only the house-robbing part of me, go easy.
But no, the unfair jerks put all of me in jail.
Facebook is likely making a lot of money off of, as you claim, something that is close to the core of what Facebook is doing. It makes $5 billion closer to a small cost of doing business.