The #2 person contributes only about 1% compared to the #1 person.
Compare to React's same graph: https://github.com/facebook/react/graphs/contributors?from=2...
The #2 person is at about 50% of the #1 person.
Compare to Ember's same graph: https://github.com/emberjs/ember.js/graphs/contributors?from...
The #2 person is at 75% of the #1 person.
Well, by "created by giants" in this instance think more of "a small team in Google/Facebook web-devs went ahead and did it, and then it caught on in the company and Google/Facebook decided to give them some more resources".
It's not the kind of "created by a large company" that something like Java or C# etc have, where there were tons of millions spend, huge 100+ person developer teams, documentation writing teams, etc and tons of paid marketing to promote the effort. That, only huge communities can compete against.
Here's from Quora about React for example:
"React was created by Jordan Walke, a software engineer at Facebook. Jordan deserves all the credit for creating React. He was influenced by XHP, a PHP-based component system that is still in use at Facebook, but also by functional programming ideas. Pete Hunt wanted to use React at Instagram, so he helped to extract React from Facebook-specific code. This prepared React to be open sourced. Later, Facebook put a team of engineers behind React and also received great contributions from the open source community. Significant contributors include Sebastian Markbåge and Ben Alpert, among many others."
So basically a one-man show for the beginning -- and similar story I've heard for Angular.