Well, IMO the press works just like police and other low level institutions.
They hire only people, who already have the proper indoctrination and mindset. Others are not even considered.
Second is peer pressure. They know what to say if they want to get ahead.
Thirdly a supervisor who tells them what's what.
Most of them can be completely ignorant about the big picture and function flawlessly anyways...
And they are more convincing, because they are convinced.