Or they correctly estimated, planned not to go out of stock and were able to succeed. Jumping from "it never shows as out of stock" to "therefore they must have badly estimated one or both of supply or demand" is even stranger a leap of thinking than the initial misconception of thinking that not going out of stock proves low demand.

In both this comment and the previous one, you're guessing at a possible explanation while writing as if you know it to be the correct explanation.

(Sorry for coming across all critical, hopefully learning what can and can't be construed from a product being in stock is worth my negativity!)