Well, being diversified is a smart business move.
There are other fun stories about the Disney Brothers that I've heard from the internets:
1. Walt wanted to make the Matterhorn. Roy said, no, too expensive. Whe Roy went on a business trip to Europe, Walt green-lighted the Matterhorn anyway, and had to explain it to Roy afterward.
2. When the secret land-buying in Florida was exposed, causing land prices to rise, there were a few more plots of land that Walt wanted. Roy said, no, too expensive. Walt said, "You see what happened in Anaheim after we built Disneyland? All those cheap motels sprang up right next to DL, making the place look run-down." Roy then said, "Buy! Buy! Buy!"