Diffidence, a false friend

I’ve recently erroneously used the term diffidence with the meaning of distrust.

Diffidence is one of the terms called false friend and, as a matter of fact, the same term in French defiance and Italian diffidenza mean “distrust”.

They all derive from Latin diffidentia "mistrust, distrust, want of confidence” but, unlike in other languages, the term in English had a semantic change:

Original sense (distrust of others) is obsolete; the modern sense is of "distrust of oneself, want of confidence in one's ability, worth, or fitness" (1650s), hence "retiring disposition, modest reserve." (Etymonline)

Can anyone try to explain how this semantic change happened in English?

This is just my best guess:

English has countless examples of pairs of words with similar meanings; in most cases, one word is derived from Latin (usually via French), and the other is derived from a Germanic root. Sometimes, there are more than two in each family, and the result is what one might call "semantic crowding" followed by words in the family either becoming more specific or more generic. This seems to be what happened in the case of 'diffidence.'

Derived from Latin: diffidence, confidence
Derived from Germanic root: mistrust, trust, distrust

Diffidence is now the opposite of one sense of confidence. It is no longer the opposite of trust because that word already had two opposites derived from the same root in mistrust and distrust. Diffidence is forced to specialize and loses its broader meaning, as do distrust and mistrust. Confidence, on the other hand, has only one possible synonym in trust, and this allows both to retain a broad semantic field without overlapping entirely.