I wonder why they refused to do it. From the judgment it seems cost may have been a factor. But their allegations were pretty thin and based on their own assertions and personally collected evidence. Couldn't they have just reiterated what they put in their pleadings (perhaps with a little help), without paying a lawyer to laboriously interview them and prepare it properly? Maybe they finally realized they'd have to take the stand (figuratively if not actually) to restate their allegations in the first person rather than passively through pleadings, subjecting themselves to cross-examination, and finally realized how deep a hole they had already dug beyond the monetary.
That is the whole point of witness testimony, I guess. Outside small claims or administrative courts, you can't just dump a bunch of written allegations and evidentiary documents and ask the court to decide everything based on the submissions. All facts and substantive inferences, except those which are self-evident, generally have to be entered into evidence by way of oral witness testimony, and one reason is precisely because putting someone in the hot seat causes people to reconsider the gravity of what they're alleging. It's sort of like signatures on contracts; it's not about preventing fraud, for which the ritual is useless, but primarily about establishing that the person took the commitment seriously. (When signatures are disputed, typically they're proven authentic not by matching signatures but by bringing in witnesses to identify the person they saw making the signature.)