As a lawyer who practices some IP law in other common law countries (UK/Aus) this case has been an interesting insight into how the US legal system works (which I have no idea about). If the case was running here then it would be split up into at least two causes of action - a copyright claim for infringement of the “works”, plus a “passing off” case. The copyright claim would be relatively straight forward - identify the actual “works” that P+F had copyright in (e.g the SC2 races) and identify where SD had used them.
The passing off case would be more complex in that you would have to establish SD was representing to the ordinary customer purchasing SC:O that the game was being made by (or at least legally endorsed by) the owners of the copyright holders of the works. That is a much more nuanced case that goes into things like the table of comparisons that P+F outlined. As part of that case, you need to establish who the “ordinary customer” is - and that they would be reasonably familiar with the original SC/SC2 to recognise all the things in SC:O that were the same or similar. I could see that being one of the weaker points of the P+F claim as SC/SC2 are pretty old games and there would be a reasonable argument that most purchasers would not be familiar with the old titles. Although it would require SD to argue they are spending all this money so as to capitalise on market recognition for an old series no one is familiar with.
The DMCA injunction was very weird from my perspective - especially the judge effectively saying any damages from the takedown were the risk SD took when it developed the game without settling the copyright first. Normally in injunction proceedings here that question would never even come up - the primary question to be considered is what prejudice would arise from granting the injunction against not granting it. In this case, is the ongoing infringement against P+F’s copyright more prejudicial than the loss of sales SD would incur by having it removed from Steam/GOG? I could see a judge say that the infringement is more prejudicial as that is a more intangible loss that is hard to quantify, whereas lost sales are just money which P+F would have to undertake to make good to SD should they lose on the main claim. But the DMCA law is very different so how that figures into it I have no idea.
Anyway, just my 2c worth from a different perspective which has no relevance whatsoever to the actual case.