There's far more to Inferno than just file size. The internal implementation is completely different. Furthermore, React Fiber and Inferno are very different in terms of internal approach.
Thanks for trying Inferno. It's great to hear that it worked out so well for you too - let me know if you have any issues or need help with anything. I'd be happy to help :)
I agree. Although I know that the React team have been spending a large amount of resources lately addressing React's performance problems. Inferno has a "inferno-compat" package that should allow it to easily replace a React app almost 1:1 without too many issues.
I've found the opposite with Knockout, especially in complex apps that make use of many observable and subscriptions. Knockout used to be great for MVVM apps, but I feel it's quite dated compared to more modern approaches both in performance and architecture.
TypeScript not only helped improve Inferno's with quality and read-ability of code. It can potentially help produce highly optimal output (bundles) with Google's Closure Compiler. In the future it may even help created optimised WebAssembly output. It's an exciting time :)
It's solving performance issues that React and other virtual DOM libraries currently suffer. This is massively important for low power mobile devices. It's not an ego driven project, all research is going back into the open-source community to make better libraries and implementations inclusion React.