I was still working in the security field (MSSP SOC) when Coinhive came out. It quickly because one of the prominent "threats" we had to deal with. All of our clients wanted any site that had Coinhive on it, whether or not the site owners added it or criminals did, blocked. It was view by nearly everyone in cyber security, including AV companies, as malware. It got a bad reputation because many sites didn't allow you to opt-in, and many didn't even tell you they were running it.