In the English language, why is remuneration pronounced renumeration?

People do mispronounce remuneration as renumeration all the time, contra some people’s denial of it here.

God knows I’ve done it, and I should know better.

Why do people do it? Because:

• The stems muner– and numer– are confusable through the oldest confusion in the historical linguistics book: Metathesis (linguistics).
• People are familiar with the numer– stem, from numerical.
• A mention of numerical in a word for how much money you get is entirely plausible, since you get an amount of money.
• People are unfamiliar with the muner– stem, for “gift”. It doesn’t show up anywhere else in English, the way numer– does.
• The stem is buried away in muni-ficent “gift-making”, without the –er-. Did you make the correlation?