That is very much the case and the policies of facebook and twitter have changed a lot, evne google removed the "dont be evil" from their ethics. People did much worse int he early days of facebook and twitter and facebook and twitter couldnt do anything because their guidelines werent made to censor things like that, let alone to particularly target a party as they do now.
These platforms haven't changed that much in terms of their policies.
If you called someone the n-word or tried to coordinate murder of some public official you would be banned.
Bannon was calling for Dr. Fauci to be beheaded a few days ago. That's what got him banned from Twitter.
Gen. Flynn was calling for public officials to be executed. He was banned.
Get it?
Twitter has not really changed that much - the public, and their expectations of 'freedom of expression' in the face of politics has changed.