You can mostly trust Swiss people to be that honest. It doesn't work like that everywhere.
That's one hypothesis. Another is that trustworthiness is a genetic trait.
Mutual Aid: A Factor of Evolution
Do you imagine the children taken into care at a young age turn into bad people just like their parents anyway?
Surely everyone thinks that trustworthiness is about poverty, inequality and values?
One plausible explanation for some of that, which wasn't analyzed there, but has some basis in other research is that things like risk-taking behavior or being prone to addiction are quite genetic.
But in any case, for many(most? all?) "moral" characteristics saying that they're only about "poverty, inequality and values" is wishful thinking. Yes, they are in part about that, but they are also in part about genetics; the answer to "nature or nurture" pretty much always is both.
"The best fitting model for 41 key studies (58 independent samples from 14 month old infants to adults; N=27,147) included equal proportions of variance due to genetic (0.50) and non-shared environmental (0.50) influences, with genetic effects being both additive (0.38) and non-additive (0.12). Shared environmental effects were unimportant in explaining individual differences in impulsivity."
So impulsivity (which is obviously closely related to your propensity to betray the trust of your fellow-man for a short-term gain) appears to be a combination of genetics and random luck (non-shared environment).
Like passing anti-minaret laws?
Societies and culture are more complex than you make it sound.