It has nothing to do with political partisanship (except to the extent that false-flagging happens or that powerful individuals have bad ideas about how to propagandize for their cause). Most people are just terrible at critical thinking, and most of the interesting claims (especially statistical ones) are simply not verifiable by random individuals.

Plenty of leftists have their own reasons to distrust media. But scarcely anyone imagines reasons why someone else would lose trust. Not that they could do anything about it anyway.

The "global left" is not a real thing. I mean, of course you can draw lines around groups any way you like, but this one doesn't offer meaningful insight.