Base line level of trust in co-worker comperence combined with either too much workload to give everything a fine toothed comb through, or too much laziness to bother.

Presented by F, slide deck created by E, based off conclusions made by D, from data formatted to look good to them by C, from work that they asked B to do, which was ultimately done by low man on the totem pole A.

All it takes is for one person in that chain to be considered trustworthy for every level above it to consider it trustworthy info by default.