Ogg is the container, Vorbis is the audio codec, and colloquially people just called Vorbis-encoded audio "ogg" because of the ogg container.

Vorbis was hit-or-miss. In some cases it did better on same or lower bitrate than MP3 encoded by LAME, in some cases worse. It also suffered an entirely new category of "chirpy/tweety" artefacts similar to what MP3 exhibits at very low bitrates, but with Vorbis they showed up even at nominal bitrates during certain complex spectral patterns. I was a vocal proponent of Vorbis back when it surfaced, but soon changed stance when realizing how unreliable it was quality-wise.

> and colloquially people just called Vorbis-encoded audio "ogg" because of the ogg container.

I would bet that the primary reason wasn't the container format, which nobody really cares about and most users wouldn't have been aware of, but rather the fact that the file extension was '.ogg'.