Just to share a bit of perspective from the Philippine side here. The Philippine president before Duterte, Aquino Jr, was more proactive in advancing Philippine interests in the area. Then, Duterte started the shift away from the US and its allies to move closer to China. The current president, Marcos Jr, is way less pro-China than Duterte.

I suspect that Duterte and his campaign was funded by the Chinese to advance their interests in the country, including the disputed area. It’s also worth noting that during his administration, the Philippines opened a lot more to the Chinese, with locals becoming resentful of the seemingly preferential treatment afforded to them. If that’s not enough, there started popping up Chinese-owned (nominally Filipino-owned) offshore gaming entities which were manned by Chinese nationals (some of them were apparently housed in terrible conditions by their employers).

There might be more anti-Chinese sentiment here after Duterte than before him, oddly enough.