Not only are they so gullible as to believe, without the slightest skepticism or effort to check it out, but, as you say, they then are useful to the people behind the green curtain as they parrot the lies to everyone else. Presenting them as indisputable facts because “experts”.
Some of these people are ostensibly intelligent, considered intellectuals (don’t get me started on intellectuals), and Nasim Taleb coined an acronym for them – IYI – intellectual yet idiot.