I think they just blatantly ignored the law, to be honest. The UK's copyright law is similar, where "fair dealing" allows use for research purposes (legal when the data scrapes were for research), but fair dealing explicitly does not apply when the purpose is commercial in nature and intended to compete with the rights holder. The common sense interpretation is that as soon as the AI models became commercial and were being promoted as a replacement for human-made work, they were intended to be a for profit competition to the rights holders.

If we get to a point where opt outs have full legal weight, I still expect the AI companies to use the data "for research" and then ship the model as a commercial enterprise without any attempt to strip out the works that were only valid to use for research.