Well, there's at least two aspects here:

Fucking Thor, PirateSoftware.

Up untill Ross posted his 'SKG is dead' video... Thor had by far gotten the most views of anyone with a video discussing SKG.

And Thor... well, he was anti-SKG, and had been spreading a bunch of objectively false bullshit about it, actual FUDD.

So... about half of Ross's video was dedicated to pointing out how Thor was wildly misunderstanding things, and fairly graciously and politely trying to correct these misconceptions.

So here's the two sort of things at play I see, in terms of 'why sudden surge now?'

1. Thor was just shown to be objectively, factually wrong. Thus, the immediate effect of this would be to reiterate and clarify and reinforce with more specificity what SKG actually is... and that could directly convince people to give a damn, to believe in Ross's SKG over Thor's misunderstandings and mischaracterizations.

But uh, almost certainly much, much more relevant:

2. Ross doing (1) created an absolute drama shit storm via the way youtube works now... which is very much just drama mongers and commentators reporting on e-drama. (1) kicked off an actual, organic, honest to god, truly viral explosion of many, many people who'd basically never heard of any of this before, mostly dogpiling on Thor for being such a disingenuous, egotistical asshole and liar, but also of course encouraging people to sign the SKG petition.

This kind of absurd, out of nowhere explosion of popularity of some topic, idea, meme, whatever, that spreads from person to person to person, from the ground up instead of top down... this is what something going 'viral' originally meant in the earlier days of the internet, 15 to 20 ish years ago.

You know, it spreads, from host to host, like a pandemic outbreak, shockingly rapidly.

These days we have everything hypermanaged by algorithms that silo you into your own content niche... and this was an exceptional enough of an event that it broke containment.

Videos like ... this entire topic/event/story... used to be what the YouTube trending tab looked like.... just totally random shit that for whatever reason, a bunch of people organically shared with each other, back when the algos were much, much more primitive.

...

Anyway... extremely ironically, a whole lot of the viral nature of this is due to Thor being just such an astoundingly massive piece of shit liar and manipulator.

He has a whole entire history of being astoundingly cocky, arrogant, dishonest, deceptive, intellectually inconsistent, rhetorically manipulative, etc, and it is genuienly... just astounding, i dont know what other word to use, to go through every single shitty thing Thor has done or said, not only in regards to SKG, but many, many other things Thor has done.

Basically, Thor is now a lolcow, a perfect person to milk by making content criticizing him, because he really is that much of an unbelievable, outrageuous idiot asshole.