My impression is that JS has led WCs for the simple fact that JS is easier to polyfill/prollyfill/ponyfill and there's a lot more infrastructure today for JS mo

My impression is that JS has led WCs for the simple fact that JS is easier to polyfill/prollyfill/ponyfill and there's a lot more infrastructure today for JS modules and JS bundling. Web Components have been a lot of trying to assemble the cart behind you while riding the (JS) horse, simply because web standards are so slow. (I'm not sure if that analogy entirely works, though in my head it adds the unsightly picture that at least some of the material you have to build the cart with is manure, and WCs being built more than partly from JS manure does sound accurate.) ES2015 modules are about at the point that caniuse statistics show them as nearly viable for production work, with HTTP/2 (or 3) deployment being possibly the last puzzle piece for a global lessened reliance on bundling for performance reasons. (Though not for simplicity of usage reasons: it's still useful to be able to drop an entire third party bundle all at once on a file host and use the thing as a single import.) Meanwhile, CSS Modules are still something prollyfilled by JS bundlers and there still isn't an official spec yet?! And "HTML Modules" is so barely on the drawing board that it would be optimistic to call what JS bundlers are doing there as anything resembling a "prollyfill" (we're to "wishfill", I guess?). (And most JS WCs are using virtual DOMs or JS-native template tools instead of HTML templates anyway.)