StrategyPage has a good summary of what is going on:
https://www.strategypage.com/qnd/phillip/articles/20191119.aspx
as for Duterte letting China take over the West Philippine sea: Obama pressured the previous president not to oppose them by sending the coast guard to stop China from harassing our fishermen, or by chasing Chinese boats building the islands. Instead Obama insisted he only go to court.
Now Duterte realizes no one can stop China and tried to make nice. But China didn't give much help, and most non elites here hate the Chinese for running the economy (which has been going on for 100 years) and making it impossible for locals to succeed.
Duterte hates the CIA because when he was mayor of Davao they got a guy out of jail and out of the country.
The CIA is busy opposing Duterte: they had chosen another candidate with CIA ties to win, and if she lost, their second choice was a crooked politician who they could influence. Instead the last minute Duterte won, thanks to grass roots support (by workers and small business owners). So the elites and NGOs and the MSM hate him: take his sarcasm out of context, exaggerate every murder as his fault (even when drug dealers kill each other, or when families whose members had died due to drugs arranged private revenge against the dealer). Even the political murders of low level mayors etc. blamed on him, even though these too were common before he took office.
The Philippines has a love/hate relationship with the USA. They don't want the US to own the country and run it, which is why the military bases were closed down in the early 1990s.
but most Filipinos like Americans and distrust China: however, they also know they can't fight China by themselves because we'd lose (a couple years ago, Vietnam fought China for stealing some of their islands, and lost that war: which is why VietNam now welcomes the US helping).