The defendants said that they had moved to dismiss, probably on statute of limitations and laches grounds. (I.e., it's just been too long, no matter what.)
It probably took the defendants a long time to put together their motion to dismiss, both because of coordination issues and because that's essentially their fundamental argument.
I'm willing to bet that the judge would be willing to dismiss in a heartbeat. But what he's doing is very carefully writing an opinion, which thoroughly demolishes the claims of the reparationists, and offers a model for other judges - because these people will refile and try this nonsense again in other courts - to use to dismiss these suits as well.
And opinions, especially large and important ones, take forever to write. So the judge probably wanted to throw the case out on its ear long ago, but these things take time.