"Mr. Ilagan, who is 59, said they watched the video 'very, very carefully' but decided to move on when the two weren't swayed. 'We didn't want to get bogged down,' said Mr. Ilagan, who works in marketing for a company that makes circuit boards."
Maybe I'm misreading it.
Another rationale is that they would have needed a unanimous opinion to overturn the patent on prior-art. And since they weren't going to get a unanimous opinion, they skipped it because they couldn't over turn the patent.
Without knowing all of the jury instructions, it hard to know exactly what happened.
I've been agreeing with your other points, but I must disagree with this specific. Absence of evidence is definitely evidence of absence. Keep in mind that "evidence" is not the same as "proof."