There was a combination of reasons. XML has plenty of problems of its own which legitimately generated a lot of hate for the format. JSON, at least superficia

There was a combination of reasons. XML has plenty of problems of its own which legitimately generated a lot of hate for the format. JSON, at least superficially, didn't have many of those because it lacked (and still lacks) a lot of features. So, for a reasonable person it wouldn't be a proper comparison, but... there's the reason number 2. JSON rise to prominence coincided with Flash dying and JavaScript hype train gathering momentum. Flash made a bet on XML (think E4X in the latest AS3 spec, MXML, XML namespaces in the code etc.) Those who hated Flash for reasons unrelated to its technological merits hated everything associated with it. In particular, that hate would come from people doing JavaScript. HTML5 that was supposed to replace Flash, but never did was fueling this hype train even more. At the time, JavaScript programmers fell inferior to every other kind of programmer. Well, nobody considered JavaScript programmers to be a thing. If you were doing something on Web, you'd try hard to work with some other technology that compiled to JavaScript, but god forbid you actually write JavaScript. But people like Steve Yegge and Douglas Crockford worked on popularizing the technology, backed by big companies who wanted to take Adobe out of the standardization game. And, gradually, the Web migrated from Flash as a technology for Web applications to JavaScript. JSON was a side-effect of this change. JavaScript desperately needed tools to match different abilities of Flash, and XHR seemed like it won't be part of JavaScript and was in general a (browser-dependent) mess, especially when it comes to parsing, but also security. JSON had a potential to exploit a security hole in Web security model by being immediately interpreted as JavaScript data, and this was yet another selling point. To expand on the last claim: one of the common ways to work with JSON was through dynamically appending a `script` element to HTML document, then extracting the data from that element, which side-stepped XHR. There was also a variant of pJSON (I think this is what it was called, but don't quote me, it was a long time ago), where thus loaded JSON would be sent as this: $callback({ ... some JSON ... }) Where the `$callback` was supplied by the caller. I'm not entirely sure what this was actually trying to accomplish beside dealing with the asynchronous nature of JavaScript networking, but I vaguely remember hearing about some security benefits of doing this. Anyways, larger point being: JSON came to life in a race to dislodge one of the dominant forces on the Web. Speed of designing the language and the speed of onboarding of new language users was of paramount importance in this race, where quality, robustness and other desirable engineering qualities played a secondary role, if at all.