This assumes journalists decide what gets into press. However, an editorial line is decided by the owners or other stakeholders (at the national level, it might

This assumes journalists decide what gets into press. However, an editorial line is decided by the owners or other stakeholders (at the national level, it might be governments), a compliant editor is hired and made aware of the line, and the editor then selects which pieces get to go in. My guess is either this process selects for journalists with the "right" views, or journalists themselves adapt their writing to keep their job (probably the latter).