Follow-up question: how has the discourse on Shakespeare's identity changed over the 20th century? AFAIK the popularity of positions thay question Shakespearean authorship really only took off in the early 20th century and has fallen in and out of vogue pretty periodically. I would be very interesyed in a short description of the history of Shakespearean scholarship.

I recommend the work of Columbia University professor James Shapiro: Contested Will: Who Wrote Shakespeare? (2010). There is literally no tangible evidence for any theory that Shakespeare was not Shakespeare. There are no documents or other physical proof for any of these theories. It's all pieced together from supposition, which someone may or may not find convincing or feel that it qualifies as proof. Why some of these theories have been supported by people of prominence, including Mark Twain, Derek Jacobi, and a couple Supreme Court justices, I've see no evidence that these theories have been given any credence in academia, either among historians or scholars of literature. One person, Roger Stritmatter, was awarded a PhD on the basis of a dissertation which embraced the Earl of Oxford as the author of Shakespeare's plays, but there has been little penetration in academia otherwise. Oxfordians (those who believe that the Earl of Oxford wrote the plays) have labeled mainstream scholars Strafordians (for Shakepeare's home of Stratford-upon-Avon) and have constructed their own academic apparatus, including a journal, The Oxfordian.