Only Mozilla dev, a die-hard NoSQL fan, prevented adoption in Firefox (he since left Mozilla) and Microsoft couldn't decide which of it's 10 SQL engines (no joke, think about MS Access, AD, Exchange, Outlook, WinFS, etc all had/have their own embedded SQL database incarnations) to use in Internet Explorer. In the end Microsoft nowadays ships SQLite with Windows. But WebSQL isn't supported by Firefox and IE/Edge - but the web users moved on, and like 99% of mobile devices have a webkit/blink based browser, and Chrome and Safari have the largest user base on desktop too.
It's not quite that simple. The WebSQL standard wasn't a "standard" at all, it was just "browsers already expose whatever SQLite they have, lets write that down!". No tests, no conformity, no way to tell if browser X supported SQLite feature Y, nothing. Just raw access to whatever SQLite was baked in. There were lots of inconsistencies.
Yeah, it was super simple and useful, but nobody wanted to do the work to make sure interoperability was a thing, in part because SQLite has very complex behavior and lots of quirks to adhere to.
Only Mozilla dev, a die-hard NoSQL fan, prevented adoption in Firefox (he since left Mozilla) and Microsoft couldn't decide which of it's 10 SQL engines (no joke, think about MS Access, AD, Exchange, Outlook, WinFS, etc all had/have their own embedded SQL database incarnations) to use in Internet Explorer. In the end Microsoft nowadays ships SQLite with Windows. But WebSQL isn't supported by Firefox and IE/Edge - but the web users moved on, and like 99% of mobile devices have a webkit/blink based browser, and Chrome and Safari have the largest user base on desktop too.