I don't see any grounds to expect this one to be unique, even though the possibility can't be excluded.
It's just bad business all around.
they're only allowed to continue to exist because of Japan's laws on cultural conservation
It’s familiar when looking at the prohibition period in the US for instance, where the mafia basically became an alcohol distribution network the day it was prohibited. Same in Japan: there’s laws on sex work, drugs, minor labor, gambling, money laundering, etc.
Yakuza groups will look at these laws and find the niches where regular businesses would be navigating minefields and blow up a thousand times, or where people will pay money for services only the yakuza can offer, and eventually abuse loopholes where they can take the money with low risk of anyone going after them.