>>ml-ano+(OP)
Not a lawyer, but as far as I understand; Certainly, the lack of significant damages would usually prevent a lawsuit because there wouldn't be any money in it, but since the amount of damages are figured out during the trial and the lawsuit alone would be damaging to OpenAI the threat of a lawsuit could be enough for OpenAI to try and settle quickly out of court. Though OpenAI would have to weigh that with against encouraging other similar lawsuits - they might think that dragging out the lawsuit might be better for them as they can continue establishing a foothold in AI in the interim even if they know they will lose and know that discovery would be damaging.
As you state, Mrs. Johansson would benefit reputationally form the lawsuit and could act as a front for other powerful institutions who would greatly benefit from the lawsuit.