Knockout.js was/is wonderful, I'm not sure why it never took off the way angular or react did. I do appreciate jsx though so I'll be looking into Solid.

As far as I could tell, around that time (and even now to some extent) the amount of activity on StackOverflow is used to measure the popularity of a project.

Angular had a "made by google" kind of logo on its website, indicating to many people that it's of high quality and worth adopting.

But Angular was also so convoluted and had so many problems that so many people kept running into random problems all the time and had to ask questions about them on SO. This signals (incorrectly) that Angular is popular, driving more people to believe it's worthwhile to adopt it.

Knockout had neither. It was not sponsored by a corporation. And it was so good that you hardly ever run into random problems.

Ultimately it was eclipsed by React and Typescript because lack of type checking for the html templates means it's hard to scale it will to large projects.

The problems with knockout were:

very hacky syntax embedded into html. Sometimes you had to even use some kind of comment notation because there was no entry point into the html to add data properties or whatever it had.

it was slow.

the observables weren't variables you could use like plain JavaScript variables

it has the same problem as React - state-based algorithms are not very good ways to solve problems (if (showDialog && !open && ranOnce). You have to keep creating more variables to represent more states instead of using normal programming language concepts, and then all of the observables ping around and become complicated.

It kinda is, but it's more than just JSX. Solid was basically born out of Knockout and is in many ways a continuation of Knockout, but it has some relatively significant changes and additions to make this approach more viable, especially for large long standing projects. JSX is more of a quality of life thing, you don't even have to use it, Solid's runtime exists completely separately of JSX and can work great without it or even potentially be integrated with other templating languages.