The article gets into the origin of the term, which surprisingly isn't just a funny turn of phrase the author of the book came up with to make fun of them:

Then a pretty well-known figure from the crypto world reached out to me over DM and said, “You know, we’ve been calling these guys the Nerd Reich for years.” And I was like, “What?” The URL was available, so I rebranded my newsletter as the Nerd Reich and announced it in dramatic fashion.

To me, the most important thing is that this is not a name I came up with. This is a name their own peers use. They are telling people what they are doing. They want people to know because they’re evangelizing to bring in more believers.

"Techbro" doesn't rhyme with "third", thus robbing it of its Nazi parallels.