Why does Esperanto use an indirect object here? It's not as if we could also have a direct object somehow relating to the verb as well as the indirect object, so why does it complicate matters?
I only ask because it's a designed language - there's probably a reason somewhere!
I wouldn't be surprised if this was a calque on German jemandem vertrauen, which uses the dative case.
A number of oddities (from the point of view of English speakers) are because a given construction was based on Polish or Russian or German or another language that Zamenhof spoke.
(For example, old Esperanto used elrigardi for "to look = to have a certain appearance", as in "she looked rich" -- presumably a calque of German aussehen. Nowadays, aspekti is the usual word for this meaning.)