Potter never lost his mojo. It's still one of the biggest draws in Orlando. Universal pretty much built Transformers "because why not?" They are bringing in Kong because they know investing their money into exciting new attractions will keep people coming back, and it has nothing to do with any sort of fear that somehow Diagon Alley, the most anticipated theme park area in the history of theme parks, will somehow fail.
While it is true that they didn't want to do loud construction during park hours, no, being in the middle of the guest area is not why it took several years to build. It's new ride tech, but barely. Swinging coaster cars have existed since the 80s. 7DMT is not a groundbreaking or technologically advanced.