Most of those authors are drive-by fixers. Go scroll through the commits list and look at the affiliations of those who are doing the regular work. But watch out, a few of them list OpenJS Foundation but actually work for Microsoft.
The Chromium stats are misleading for the same reason. Almost all commits are made by Googlers. There is a long tail of contributors over the years outside of Google but that doesn't mean their contributions are equally sized.
Yes, but there are 15000 forks of the electron by individuals, even with contributions being not equal, it is still a community project owned and used by individuals and smaller groups all around the globe, not only Google or Microsoft. The same applies to Chromium. The fact that MS is the biggest maintainer now is not a coincidence because it is in their genes to constantly try to take over the good stuff to commercialize under their brand.
The Chromium stats are misleading for the same reason. Almost all commits are made by Googlers. There is a long tail of contributors over the years outside of Google but that doesn't mean their contributions are equally sized.