I'm not very familiar with htmx but at first glance it seems similar to Angular. I thought Angular lost favor because of all the extra attributes and boilerplate. What makes htmx different?
HTMX is a layer on top of server-side rendered HTML that gives you near-SPA-levels of interactivity without having to build a standalone SPA.
HTMX is a polar opposite to Angular in terms of complexity, for one.
htmx is based on the ideas of hypermedia, you can read the first chapter in our book on the topic here:
https://hypermedia.systems/hypermedia-a-reintroduction/