Earlier quoted context omitted.
Right, and in exchange users received rather a lot of services for free... photo and video storage etc as just one example, Llama is free to use, etc etc. While I've no sympathy for mishandling private user data as Meta has of course been guilty of in the past, I think users getting 16 years of free service in exchange for their public posts being used in this fashion is not that bad of a deal.
You get photo/video storage worth a fraction of a cent. Llama doesn't have a free to use service. People got 'free service' in exchange for putting ads around content not for this. It's a terrible deal no one asked the users if they want to agree to. It's visiting a website and saving an image and claiming the website owes you for storage.
The real question is whether the agreement that was made between them and their users during 2007-now covered uses like training AI, but most likely it was a very broad "we can use your data how we want" type of statement and that agreement wasn't fought (or fought hard enough?) back then.