"trusts" = "ufa".
"wierzyć" is rather "to believe something specific that was said". trust is something more general.
In what way is rolnikowi not a direct object? It is surely the direct object of believes.
Take a look here: https://dictionary.cambridge.org/pl/dictionary/english/indirect-object
Unless that really only is called that if there are two objects in the sentence... in which case we probably need to explain it a bit differently, because it's still Dative in Polish anyway.
The trouble for me is that Polish seems to define the cases differently to the system I learnt, mainly from Latin in which the accusative is the direct object, the genitive indicates possession (in a very broad sense) and the datives means movement towards. Polish turns all this on its head with direct object sometimes needing genitive and some verbs needing a dative object as here.