Most of which is barely maintained and low quality.

For example, just recently:

https://linuxiac.com/libxml2-becomes-officially-unmaintained...

But even before it became officially unmaintained, it was already quite unloved, and it's one of the most used xml library.

We are not in the peak Java/J2EE era anymore. Pretty much nobody is going to willingly work on the foundations unless they're getting paid because the majority absolutely loathes XML and would not see maintaining XML libs as fun, and guess what, they're not? xslt also got removed from web browsers because nobody wants to maintain those libraries. And corporations like Google don't want to pay a dev for those either.

https://developer.chrome.com/docs/web-platform/deprecating-x...

Meanwhile the tooling around JSON is as healthy as it's ever been, with very efficient implementations in most common programming languages and multiple SIMD impls in C, C++, Rust etc. People actually want to work on this.

I don't understand why that is relevant; as long as there is a minimum level of tooling, libraries and support for their choice, what benefit would JSON bring over XML? I don't see a clear reason for one over the other.

Honestly, I'd have the same question if they chose JSON and someone asked why did they choose JSON over XML - Why wouldn't they?