Maybe. It could be that trust is now variable by phrase. Possibly less competitive (or less monetised, if there's any difference) KW phrases, require lower trust standards.
Whatever criteria used for variable trust levels, this differential would have two effects, which could be easily confused:
1) High trust sites get swamped as low trust sites get propelled above them on "low trust allowed" phrases.
2) Lower trust sites lose rankings as they no longer make the grade on "high trust required" phrases.
On the crappy SERPs, are you looking at vanity or long tail phrases?