They didn't fork GHC. They wrote a new Haskell compiler to target a pre-existing runtime that existed inside the bank. For various reasons related to the runt

They didn't fork GHC. They wrote a new Haskell compiler to target a pre-existing runtime that existed inside the bank. For various reasons related to the runtime that meant the language had to be strict. Mu's creation was, in fact, a step away from legacy.