https://www.maritime-executive.com/article/subic-bay-regains-its-importance-as-a-forward-base
This
is just further evidence that the United States plans to stay in the
Philippines and return the archipelago nation to its former status as
a major host for US forces - a tip of the American spear in the
strategic South China Sea.
Subic
Bay was abandoned at the conclusion of the Cold War. The US
relationship with Manila had been put under stress (largely due to
the US backing of the 1965-1986 Marcos dictatorship), and there was a
push to downsize and shift to other theatres. The straw that broke
the camel's back was the 1991 eruption of Mt. Pinatubo, a devastating
and destructive event that left much of the region buried under ash.
The clean-up costs and logistics were going to be terrible - the
Pentagon decided it was time to walk away. Clark Air Base closed in
1991 and Subic Bay in 1992.