Can't really get more popular than that.
I think you meant to say, "why didn't it get more popular for _pirates_"? Because pirates are purists and prefer lossless codecs (ie, FLAC), and even when they wish to use lossy, Opus being locked to 48khz (to reduce implementation overhead for low power SoCs) kind of pisses them off, even though Opus's reference impl includes a perceptually lossless resampler (ie, equivalent to SoX VHQ, the gold standard, and better than the one in Speex).
Examples of users: Discord, Whatsapp, Jitsi, Mumble, Teamspeak, Soundcloud, Vimeo, Youtube (but not Youtube Music), in-game voice chat on both the PS4/5 era PSN network and the Xbone/XSX era Xbox network, the new Switch 2 in-game voice chat, games that use Steam's in-game voice chat (ie, TF2), all browsers (required to impl webm and webrtc), most apps on Android that have their own sound files (incl. base apps in Android itself). Windows and OSX also have native OOTB support for Opus. Some "actual" VoIP platforms use Opus. Some phone calls routed over the LTE phone network use Opus.
It is also standardized by the IETF as RFC 6716, and most for-audio SoCs support Opus natively as part of their platform SDKs.
You're not going to find anything more popular than this.
I get Opus on Youtube Music, both in Firefox on Windows and in the Android app.
Do they find these by monitoring the brokers of zero days or analyzing devices of people who are being targeted?