The shipwreck perhaps corresponds with his first bankruptcy, with which it coincides in point of time, having happened just twenty-eight years before.

If Defoe had a real man Friday, who had learnt all his arts till he could practise them as well as himself, the fact might go to explain his enormous productiveness as an author.

But I doubt whether the allegory can be pushed into such details.

Defoe's fancy was quick enough to give an allegorical meaning to any tale.

He might have found in Moll Flanders, with her five marriages and ultimate prostitution, corresponding to his own five political marriages and the dubious conduct of his later years, a closer allegory in some respects than in the life of the shipwrecked sailor.
The idea of calling _Robinson Crusoe_ an allegory was in all probability an after-thought, perhaps suggested by a derisive parody which had appeared, entitled _The life and strange surprising adventures of Daniel de Foe, of London, Hosier, who lived all alone in the uninhabited island of Great Britain_, and so forth.
If we study any writing of Defoe's in connexion with the circumstances of its production, we find that it is many-sided in its purposes, as full of side aims as a nave is full of spokes.