China's reserves were larger, but are still the largest (more than twice the #2 country).
I suspect some of them were used to finance some large infrastructure projects as well as the Belt and Road initiative.
I have a theory about our different utility reliability experiences. Dongguan is a major production hub. In town utilities were very reliable even when I first arrived, but out in the village, they were less so. The village sits among factories. When clothing was the main production item, a momentary or even hour-long power interruption is just an annoyance. As more and more high tech production comes online, reliable power is much more important. Also, an overseas investor won't freak out if a clothing factory loses water or power for an hour. Coming into a cell phone or computer components factory and seeing the basic utilities take an unscheduled break is a lot scarier. So, the city (and the whole Pearl River Delta) pretty much had to prioritize getting utilities upgraded.
If your town lacks high tech manufacturing, it may not consider extremely high utility reliability to be a top priority.
As for "Belt and Road", someone at the top figured out that the biggest hit to China in 2008 was WalMart buying less stuff from China. Giving countries with growth potential a leg up as well as some reliable roads and port facilities gives China a wider customer base. I haven't examined all the details, but I'll wager some of the beneficiary countries are also signing contracts to provide raw material to China. This, in combination with increased emphasis on domestic consumption further insulates China against fallout from US and European economic downturns.
How China pulls something as massive as it's economy forward? It's been 40 years since the "Opening" was announced. If China tried to bring the whole country forward at once, there wouldn't have been enough resources. Instead, the opening started with Special Economic Zones and carefully paced relaxations of other rules. When the special zones worked, they expanded. Infrastructure projects focused on turning places like Dongguan from sleepy little towns into industrial workhorses. Then, development was slowly expanded from the coastal areas to points farther and farther inland, with road and rail upgrades timed to support these.
Obviously, there's more to it, but this at least gives an idea of how at least some of the larger pieces of the puzzle fit together.