Why would the Outsider Artist Justin McCarthy sign a painting as by Rubens ?

A cruise ship lounger on deck with a bright red sunburned face. But why would Justin McCarthy sign a painting as by "Rubens" Justin McCarthy suffered what has been called "a major nervous breakdown" from 1917 to 1921 or so, some years of which he was in an institutional setting.This occurred shortly after his well-to-do family left him (as a young man) to wander the Louvre. The story of how he painted himself back to reality has been often told. But the signature? During his recovery McCarthy signed numerous names to his work, but Art scholar Nancy Green Karlins Thoman deserves the credit for revealing some of McCarthy's hand written notes from the time period in her dissertation “Justin McCarthy (1891-1977) The Making of a 20-century Self-Taught Painter.” In a sketchbook from 1919 - 1920 he jotted down his impressions of the great artists noting their characteristics as he remembered them. Among them Van Dyke (sic) Rembrant (sic) and Whistler. And for Rubens? McCarthy wrote “Rubens - red agent, ruby red.” He certainly couldn’t have been intending to copy Rubens with a woman on the deck of a steamer but in his somewhat troubled mind it made sense. To the artist, it was the color red. Years later his friend and patron Sterling Strauser had McCarthy go back and sign many works. Hence, his own signature appears as well! Justin McCarthy Untitled (Woman on a Ship) circa 1920 - 1930? Collection Jim Linderman