The same fact lands differently depending on who’s saying it, and that’s not irrational, it’s a real, studied variable.
Whether a claim gets believed depends heavily on who’s making it, not just what’s being claimed. Source credibility: built from perceived expertise (does this source know what they’re talking about) and perceived trustworthiness (do they have a reason to mislead me), was shown experimentally to shift how persuasive identical information was, depending only on who the audience believed said it.
This is also exactly why the finding gets weaponised: if credibility itself can be manufactured: a lab coat, a celebrity endorsement, a suit and a diploma on the wall, an audience’s trust can be won without the underlying claim earning it on the merits.
Source: Hovland, C.I., & Weiss, W. (1951). “The Influence of Source Credibility on Communication Effectiveness.” Public Opinion Quarterly, 15(4), 635–650.