Sycamores are super long-lived. Willow are usually the opposite.
In the case of the sycamore it is under attack from an insect introduced to the US via goods imported by ship on wooden pallets, as I recall.
All of which puts California in a sort of Catch 22. The inescts killing these trees are readily controlled by neonicitinoid pesticides, but neonicitinoid insecticides are frowned upon by the powers that be in California because when used in other situations they kill beneficial insects as well.
The California Sycamore, like the Valley Oak (largest oak in the world) sends a tap root down to the water table. It’s often as much as 100ft deep.
It’s how they take up water. Not from surface roots.
If the water table drops faster than they can sink the root, they die. And millions have during this drought. It’s a genuine tragedy.