(This is also, why scripting languages were prevalent server-side with slow hard disks: loading and compiling a Perl script was faster than loading a massive binary. See also the 2MB Java Hello-World.)
Wasm is a good example of a bytecode format designed for small code size. Though I expect wasm may often still be larger than equivalent js just because it's so much lower level. But there's no reason you couldn't design a compact bytecode format with high level semantics, and I would expect it to beat any human readable format.
A far, far better choice would have been some orderly structuring of the semantics of parsed and interpreted code. What the compiler has internally after digesting the source, but before generating code. Choose some schema and emit json or something. That would have been a game-changing choice some decades ago. But no we got saddled with byte-code and a billion dollars has been spent mitigating that disaster.
You mean the parsed Abstract Syntax Tree; AST.
The next step would obviously be that people choose to start programming directly in the AST form. And now you have created Lisp.