You mean before or after all the sites updated their ToS it so that they were legally in the clear to sell user posts to AI training companies?
The ToSes would generally have a blanket permission in them to license the data to third-party companies and whatnot. I went back through historical Reddit ToS versions a little while back and that was in there from the start.
Also in there was a clause allowing them to update their ToS, so even if the blanket permission wasn't there then it is now and you agreed to that too.
Learning from things is a very obviously a completely different process to feeding data into a server farm.
It is not very obviously different, as evidenced by the fact that it's still being argued. There are some legal cases before the courts that will clarify this in various jurisdictions but I'm not expecting them to rule against analysis of public data.