Why did dr.Seuss become an author and illustrator?

The Cat in the Hat developed as part of a unique joint venture between Houghton Mifflin (Vanguard Press) and Random House. Houghton Mifflin asked Ted to write and illustrate a children's primer using only 225 "new-reader" vocabulary Words. Because he was under contract to Random House, Random House obtained the trade publication rights, and Houghton Mifflin kept the school rights. With the release of The Cat in the Hat, Ted became a children's book author and illustrator.