I have heard people argue that Shakespeare could not have written the great plays attributed to him because the Stratford man was too ignorant, uneducated, inexperienced. But that is to make two errors: to discount genius, and to neglect the fact that nobody else could have written them - because Shakespeare's work is far above that of any of his contemporaries.
There is indeed a mystery about Shakespeare, because so very little reference to him is made in documents - some have (plausibly) suggested that Shakespeare deliberately 'kept low' because if his family connections with notorious Roman Catholic counter-revolutionary traitors against the Queen. Whatever its cause; the paucity of contemporary reference to Shakespeare has left a vacuum into-which rushed the idea that he did not author 'his' plays.
By contrast, a great deal is known about Isaac Newton. Yet - by the standards of arguments against Shakespeare - there is even stronger evidence that Newton could not have made the mathematical discoveries with which he launched his international career.
In his biography of Newton, Never At Rest, Richard S Westfall shows meticulously that Newton was almost ignorant of mathematics until less than 2 years before he began publishing major breakthroughs in the subject. Clearly, this is impossible - so Newton couldn't have done it - especially as Newton had pretty much failed his degree exam, and only passed by an irregular 'back door' route. So he was clearly 'a duffer'.
Of course, I am joking! It is precisely the fact that Newton did the impossible, and learned mathematics so rapidly and thoroughly that within a couple of years he surpassed everybody in the world, which demonstrates his supreme genius even in an age of genius. He then went on and did much the same with physics.
Newton was not a 'front' because there was nobody - and no combination of people - who could have done what he had attributed to him.
Shakespeare likewise, in his plays apparently demonstrated more wide-ranging and detailed knowledge than it was plausible for him to have acquired by normal means - but then, he was not a normal man...
Note: My book on genius - The Genius Famine - is available free online.