Short answers, pulled from the story.
J. Thomas Looney changed everything when he released Shakespeare Identified in Edward de Vere, 17th Earl of Oxford in 1920. This single volume made Oxford the most popular anti-Stratfordian candidate and launched the modern movement.
The death of Edward de Vere occurred in 1604. Critics often cite this date as compelling evidence against the theory since the generally accepted chronology places the composition of approximately twelve plays after that year.
Roger A. Stritmatter conducted a study of marked passages found in Edward de Vere's Geneva Bible which contains 1,028 instances of underlined words or passages. He believes about a quarter of these marked passages appear in Shakespeare's works as either a theme allusion or quotation.
Looney declared that the late play The Tempest was not written by Oxford because its style and dreary negativism were inconsistent with his soul. Later Oxfordians have generally abandoned this argument and now prioritize severing the connection of the play with the wreck of the Sea Venture.
Mainstream academics argue that the theory is based on snobbery and that anti-Stratfordians reject the idea that the son of a mere tradesman could write the plays. David Kathman writes that their methods are subjective and devoid of any evidential value because they consistently distort and misrepresent the historical record.