It’s very much to do with this government in their fight to break the unions. Thatcher did it to the miners in the 80s, Murdoch with the press unions.
Having a 20th century style trade union which supports people who don’t have privilege is very much against Tory principles.
If the Tories in their guise as the DfT get away with this, it’ll spread to Southeastern, SWT who still have guards on their local metro services in SW London etc.
It’s no coincidence that Chris Grayling rejected TfL’s offer to operate Southeastern while a Labour mayor is in power. It’s everything to do with ideology and nothing to do with common sense.