That's odd, MathJax does not render the math as images (unless you configure the output format to be SVG, but even that is not the default). Do you have a memory of (or can retrace) how you ended up with that unusual configuration?

(MathJax's output formats, namely HTML+CSS, SVG, MathML — see https://mathjax.github.io/MathJax-demos-web or https://docs.mathjax.org/en/latest/output/ — are strictly a superset of KaTeX's output formats, namely HTML+CSS and MathML: https://katex.org/docs/options.html )