Yeah, I gotta say, some folks have much faster eyes than I do. I honestly thought he was damaging the light sabers. Then the lightsabers popped back on. So, we have zero explanation for why they turned off, not even a hint, then the jedi kinda shrug and their lightsabers turn back on. Again, zero explanation. And folks are wondering why I'm confused? Nearly fifty years of Star Wars and this hasn't even been hinted at as a possibility, unless I've been reading thirty or forty year old novels. Never seen before.
You'd think that maybe, just maybe, if there was this material that could short out lightsabers, someone might have used it/mentioned it before now. I mean, didn't we just have an entire couple of seasons of Mandalorean that spent significant amounts of time explaining Beskar? It's not like that spear just came out of nowhere and started blocking light sabers.
But, hey, sure, let's bomb something like this into the middle of a series with zero foreshadowing, because, of course, we can rely on a bajillion Youtubers rushing to the explanation.