This is a slightly odd take, technologies can gain rapid growth at any stage. Take python for instance it was a niche language for a majority of its lifespan but then it suddenly got crazy popular.

Can't it be a segway into other FP jobs?

Unfortunately FP jobs seem to be niche and extremely location dependent. Python and Javascript are winning the market, FP had a slight increase in interest but sadly fading, job wise anyway.

I say this as someone who didn’t know much FP 8 years ago, invested a bunch of time learning, picked up a few good jobs using it but now cannot get hired due to no FP specific work in AU and non FP roles seeing 8 years of FP get a bit weary, despite a decade of Java, Python, PHP etc before my FP roles.

ELM is a great Trojan horse into learning FP if you want to learn FP though.