I'm not knowledgeable about the engineering, but on the political side it's an attempt at integrating HK and Macau physically and make everybody understand it's

I'm not knowledgeable about the engineering, but on the political side it's an attempt at integrating HK and Macau physically and make everybody understand it's now PRC land, quite overbearingly. There's been a crackdown on "disent" over there. The government also seems to be betting on pump money into giga-infrastructure (see Belt and Road Initiative) to keep slowing growth at bay.