I want to know the answer to the following question:
How or why do variations enter a witness text?
All the background I'm provided with is that "The process of textual criticism seeks to explain how each variant may have entered the text, either by accident (duplication or omission) or intention (harmonization or censorship), as scribes or supervisors transmitted the original author's text by copying it.". Is that enough to answer the question?
Answer: yes