Haskell has been around for 29 years. It's really not a fair comparison.

I never said you have to learn category theory or any math with Haskell either. My learning curves I mentioned were strictly practical (mutation/effects, state, lenses, more than basic types etc).

The quality and quantity of books, tutorials, community, libraries, etc plays a big role in any languages learning curve no doubt. I believe this is something that could still be greatly improved in Haskell.

But at the same time I don't think it's surprising that Rust was able to get those all up to Haskell's level of quality in a short time. Rust also has far more analogies and similarities to what most C/C++/Go/Python/Ruby users have been exposed to which makes the initial get-a-basic-script-working far easier.

So I'm not dismissing Haskell like it's destined to unpopularity just because it's hard. The larger investment in docs, websites, libraries, and similar languages like PureScript/Elm the more popular Haskell would be.

Rust had a bunch of smart marketing-friendly people join in over the last couple of years which took it from a niche systems language into something far more mainstream. Other successful languages had similar growth patterns early on while Haskell people were comfortable with it's fringe academic position for a long period (which it seems to have grown out of finally). Haskell could still achieve a similar trajectory but adoption by early-adopter non-academic developers will be critical for that growth. Even if that must include the trendy Ruby/JS they tend to look down upon that group knows how to sell a language to the public and make it practical.