The risk with this type of developer is they often prioritize their toolset and amazing code over the actual businesses needs. I’ve seen it lead to the wrong tool being used for the job.
A couple years later when these devs move on the business has a harder time maintaining the code they leave behind.
There are always drifters to be hired, which has some value.
But I'll take hiring (and the implied difficulty in finding) a dozen of those kind of Devs over drifters all the same.
If they weren't passionate, why use an esoteric language? If you want an easy time, something mainstream will be easier. It isn't like anything is actually impossible to implement in C; there are just trade offs in number of bugs and time to implement. Both of which are minor impediments vs algorithm and program architecture. Anything newer than C is just bonus modern features.
Because it is kitsch. Ruby suffered this fate in the mid 00s IMHO. It gained a lot of traction because of Rails and suddenly the recruitment space is flooded with hacks and bootcampers.
The more esoteric a language is, I find the more _passion_ the average developer has for that language, it's libraries, and tooling.
Now I'm not saying the passionate Java and/or C# devs don't exist - they certainly do, C# is my bread-and-butter and I like to think I still have a flicker of passion for my work - only that there is a vast ocean of driftwood developers making it more difficult to find the sharks.
Haskell (my perception of), for example, has demonstrated some of the strongest devoted (to themselves _and_ Haskell) developers I'm yet to meet. That market is just nothing but developers who love their toolset and just want to write and learn amazing code.