Not solely. Opus is a hybrid of the SILK codec, which is more for speech, and CELT, which is more aimed at music. It can seamlessly switch between the two methods and use them simultaneously: https://wiki.xiph.org/OpusFAQ#Why_not_keep_the_SILK_and_CELT...
The main goal was streaming (of both music and speech), and hence, low latency. Matching or bettering high-latency codecs (like Vorbis) on quality was just a bonus, and I believe somewhat of a surprise to the developers when listening test results came out.
> Opus is a totally open, royalty-free, highly versatile audio codec. Opus is unmatched for interactive speech and music transmission over the Internet, but also intended for storage and streaming applications
The main goal was streaming (of both music and speech), and hence, low latency. Matching or bettering high-latency codecs (like Vorbis) on quality was just a bonus, and I believe somewhat of a surprise to the developers when listening test results came out.