After Walt Disney's untimely passing, Roy Disney began making his mark on the company. The very first thing he did was kill off Walt Disney's vision for EPCOT. The "City of Tomorrow" was gone. In its place was Roy's vision for a "Vacation Kingdom" filled with revenue producing enterprises like theme parks and hotels. Perhaps his most daring decision was to change the name of the project to "Walt Disney World" to fully "honor" his brother's vision, despite Walt's actual vision being replaced with that of Roy Disney.
To the chagrin of Walt's creative team, Roy began planning out what he thought would be a money making enterprise. This time the company would focus on the things that were revenue producing, like hotels, and skimp a bit on the actual attractions. DISNEYLAND had been built up over the years, right? This so-called "Magic Kingdom" would be the same. If Walt had done things the same way at DISNEYLAND, he would have kept building the DISNEYLAND Hotel instead of getting Jack Wrather to do it. Where would the money have come from? Maybe he would have waited to build Tomorrowland.
Roy was willing to spend some money, however. Take Cinderella Castle. He wanted to build a larger castle to show how the company was now bigger than before, despite the fact that Walt built the castle at DISNEYLAND to be the perfect size in his mind. Walt wanted a cozier castle because it was not imposing for children to look up at and in his mind only tyrants built huge castles.
Meanwhile, they built a Fantasyland that mirrored the one in DISNEYLAND. Which was the one thing that Walt had wanted to change. (DISNEYLAND eventually got an upgraded Fantasyland that matched Walt's dreams in 1982.)
So Roy Disney's vision opened to the world in 1971. This was the vacation kingdom of Roy's dreams- a place where revenue would rule the day.