These parties "also concealed the existence of Mr. Lee's default judgment in CA"
That sounds a little far-fetched. Someone went to the door of his home. Gave the papers to a person who answered "yes" to being Rob Monster, and who also matched his physical description:
It looks more like the problem was his late-breaking realization that he wasn't going to be able to rely on claiming that he "Robert W. Monster" is not "Rob Monster" named in the lawsuit that was served on him.
So, could it have been an impostor? Rob was actually away somewhere, and someone matching his description was hidden in the bushes to show up at the front porch when the process server arrived to deliver the papers?
No, he decided to try to set aside the default judgment on the grounds that he is not "Rob Monster". The thing is, if he's really not "Rob Monster", then why is this "Robert W. Monster" guy showing up to set aside a judgment which he claims is not against him?
There seems to be quite a difference of views on the subject of whether "Robert W. Monster" had reason to believe that "Rob Monster" was being sued, and that "Robert W. Monster" might be held accountable for it... As noted in the opposition to his motion...
...
...and it goes on.
The judge denied Rob's motion, or Robert's motion, as having insufficient evidentiary support (i.e. none) to rebut the process server's declaration. It's not clear that he tried to challenge the process server's declaration, because it seems the thrust of his argument was that receiving papers to the effect that "Rob Monster" was being sued was not proper notice to him "Robert W. Monster" that he might be held accountable for a judgment against "Rob Monster."