So just checked this link. I also have been tracking these guyz really long ago. There has been several methods for this one, best one is to have a strong adx partner or getting an old and strong adsense account. Once you have enough organic + paid traffic + strong adsense, google stops caring for a while. I have done hell lot of content arbitrage with these. As old traffic sources are being patched like discover and webstories guyz are now running ads on fb to gain traction. The redirect traffic usually works with google adsense as google will consider the traffic coming from 301 url. And on the page there is something prelander type of stuff going on so people can click to see. Also they have rewarded ads enabled so it helps generate more revenue.
just checked ads.txt on both urls and the accounts seems to be atleast 2-3 years old.
main website
google.com, pub-3166750233652041, DIRECT, f08c47fec0942fa0 --> fairly old
google.com, pub-6030264180774141, DIRECT, f08c47fec0942fa0 --> fairly new
google.com, pub-1970861474735428, DIRECT, f08c47fec0942fa0 --> very old (can be adx)
google.com, pub-5386681437446122, DIRECT, f08c47fec0942fa0 --> fairly old ( can be indvidual account)
just try to copy the prelander, put your ad tags there but you need strong adsense.