Even if you ask every person to walk the earth what they want, that won't allow you to know future demand. The market shifted largely from hub-and-spoke to point-to-point during development. Without the benefit of hindsight, it must have looked like a solid bet.
A380 was also the result of "customer interviews", but after all the years needed to complete the project the customers have changed their mind, preferring direct flights over hub-and-spoke flights.
When A380 started, and even when it was delivered first, the answers to "what will be the preferred form of airline transport network organisation, in detail" was not yet fully answered.
And A380 simultaneously served as base (in many critical areas) for the quite quickly made A350 et al
After launching, then dropping, the A380. Perhaps they didn’t do enough customer interviews there.