To some extent it was both. The web made programming relevant to a much broader audience, and JS is much more approachable than other popular languages from that time (eg C++).
JS appeared at the same time as PHP and Ruby. Python was 4 years old when JavaScript was first released. All those languages are about the same level of complexity.
Now the latest boom if JS is its use in full stack applications with Node.js One language, everywhere. Also supersets like TypeScript for validation and specificity.
