But as for my 2 cents: most of the startups you're reading about were created 3-5 years ago when Node was peaking. I think it's still a popular choice for new startups but maybe not as much as it was a couple of years ago (you now also have Go, Elixir, Deno and all the boring tech like Python/Java/.net). That's what happens with a lot of tech, it has a crazy hype cycle, it peaks and then it stagnates or declines.
It's the hot new shit and you wouldn't want to be caught dead using boomer tech like Rails even if it's more stable, the eco system is bigger, it's easier to find talent for, etc.