I would argue that Skyscrapers at that time were a very common building. Starting in the late 1800's through the 1930's, there were dozens of skyscrapers being built in New York and around the US. During this same time frame, the title of "tallest skyscraper" changed hands 11 times meaning creating buildings of exceptional height wasn't uncommon. I think you also need to look at the crew to see why it got created so fast. In the initial phases, they had 600 men who ran two 12 hour shifts. At it's peak, the crew was somewhere around 3,500 workers. All these factors combined (plus the enormous amount of money to finance it all) is why it got done so fast.
I agree that people like us will always go in massive numbers and Disney is letting Universal play catch up. Let me expand on why I think Universal is not thinking long term.
- They currently have all their equity tied up into Harry Potter. No doubt this has made them an unfathomable amount of money and it really is a engineering marvel but what happens in a year or so once the next fantastic beast movie is done and no new entries are being added. The only planned changes post the next movie are a retooling of the dueling dragons coaster and some Christmas / Light shows on the Hogwarts castle. As the next generation grows up without Harry Potter being as big as it is now, I can see problems. This is where I think building lands around concepts makes much more sense than franchises.
- The current lineup for 2018 is a fast and the furious ride, a Jimmy Fallon attraction, and some new hotels and expansion of Volcano bay. None of these would drive me to say that I absolutely need to go to Universal on my next trip to Florida. The Super Nintendo World for 2020 looks really interesting and will be successful and that's because it relays on a theme as opposed to a specific franchise. This would allow them to create new rides whenever they want and keep it fresh which is what I feel that should be doing for long term success.
- They purchased a huge portion of land (over 400 acres) back in 2015 but so far haven't announced any preliminary plans for it. If you are buying a huge amount of land like that, the natural assumption is another park. The fact that nothing has been done with it so far to me suggests that they might not have a fully fleshed out plan which means it just sitting there not making Universal money