These sites do get taken down relatively frequently, but their owners are masters of ban evasion and quickly reopen them under another name or sell them to some

These sites do get taken down relatively frequently, but their owners are masters of ban evasion and quickly reopen them under another name or sell them to someone else who does, as it recently happened with a certain anime site formerly named after a green-haired swordsman. There usually is a hefty layer of indirection and obfuscation between the sites and the actual content served, presumably to make these moves easier (moving a frontend is certainly much easier than moving a multi-terabyte library of pirated media) while also preventing other similar sites from leeching off the same content. The smaller ones additionally tend to employ fairly aggressive SEO techniques, which is why finding them is easy despite the continuous takedowns and name changes; the largest ones seem to rely mostly on word of mouth, just like their torrent counterparts.