I think Jimmy carried 4chan lingo here first. I know he had used 'cuck' first and I remember searching his history to find a bunch of 4chan-related spicy sentence enhancers.
I never even went to /pol/ until moot did a thing where he turned it into an official cuckolding forum where some Cuckolding Princess audio would play nonstop, encouraging all of the other boards to raid /pol/ with cuck memes and porn. I was mostly a /mu/ guy for non-metal discovery purposes, and a bit of /vr/ (retro video games). The event caused an uptick in 'cuck' strong enough to be seen on Google Trends, and it only grew from there to the point that it's common political parlance.
It is a great word even with its meaning put aside. Rhymes with fuck, starts like cunt, not far from cock. The sexual, gender, and racial undertones perfect it as a top-tier slur. And funnily enough, apparently in the 1950s there was a period where it gained traction in politics as well, so you can't even say that it's just a forced meme.