The Hong Kong government has been pretty angry with Disney for several years, and rightly so. Disney announced a unique and more lavish park, but mid-way through design switched to the low budget all-clone mini-park that was built in 2005. This included the budget conscious decision to forego a unique castle for a clone of DL's.
The park opened, like DCA and WDS, to a bit of a thud and has struggled ever since. The government made Disney pay for the entire first round of expansions (Grizzly Gulch, Mystic Manor, Toy Story Land) when ordinarily, they would have paid 53% in accordance with the ownership split of the park (as Hans noted, Disney owns 47%).
The expansion didn't make a huge difference, but the park has been doing better. Iron Man Experience, which opened last year, has done more than any other new attraction the park has ever had to bring in people (Marvel is big in China).
Then comes the 2015-2016 time period, when details of SDL are released and that park opens. HK knows Disney went full out on SDL, spending billions on a big, flashy and almost entirely unique park. They're now livid that Disney cheaped out on them.
There are culture issues at play here as well. The tension between HK and the mainland is palpable and flammable - remember the big wave of protests a couple years ago re: democracy - and pride/saving face is a big part of Chinese culture. HKDL is an embarrassment where it should be a crown jewel. There were more than a couple loud voices last year in HK who advocated shutting the park down and calling it a day.
The newest round of expansions is meant to quell HK concerns of having a lesser park than Shanghai. The Moana show, the Ant-Man ride and eventual Avengers E ticket, the Frozen land - all things that will be unique to HKDL, and hopefully, big draws.
The castle became a particular sore point when SDL's was revealed. The world's biggest - so imposing, so grand - and HKDL has a sadsack copy of the first tiny castle no one thought worthy of replication for 50 years. Hence the demand for something more impressive.
We American Disneyphiles have criticized the SDL castle, and the art for HK's new one, a great deal. You have to remember though - these castles aren't for us. They match Chinese sensibilities, and match them well. They are perfect for their intended audiences, so it's not of much consequence to WDI what American superfans think of the designs. The Chinese like huge things that are blingy, and that's what Disney is giving them.