As someone who has never trusted institutions, nor seen any particular reason they should be considered trustworthy, the contrary question feels more interesting: why did people in the past have so much faith in powerful organizations? Was it a function of centralized mass media? Given the a US-centric nature of the research, was it something about the depression/WWII/post-war boom experience?
I'd suggest maybe just the nature of organizations becoming more corrupt over time. When an org is younger more of its focus is still put towards the task it was originally created to perform, but the longer they exist the more bureaucracy and corruptness sets in, the most institutionalized they become, the more they put their effort into just spreading their influence and enriching themselves rather than performing their original task.
Sometimes at points in their history an org can reform itself and revert back to an earlier stage, but at this point I personally feel that most major institutions have been around long enough that they've effectively become corrupt beyond the point of reform, and just need to be replaced.
Because no man is an island and trust in institution is how our society evolved. Trusting that when I buy food from market, it is safe to eat, trusting that when a sentry says the enemy is coming, that we prepare. Sure, they fail at times but it's vastly superior to the alternatives.
I don't get this notion of 'trustless' as a feature. We should want to trust more. 'Do your own research' is such nonsense in so many ways - I don't want to re-invent periodic table or the that the Earth is round. Sure, the experts can be wrong at times but for one to challenge that, one has to first be an expert in the same domain.
I have always hypothesized that it's because these traits have helped our parents to blend in and survive (and bloom) in slavery and corrupted civilizations. I have nothing to back it up of course.
